The
health effects of tobacco are the circumstances, mechanisms, and factors of tobacco consumption on human health. Epidemiological research have been focused primarily on
tobacco smoking Tobacco smoking is the practice where tobacco is burned and the vapors either tasted or inhaled. The practice began as early as 5000–3000 BC. Many civilizations burnt incense during religious rituals, which was later adopted for pleasure or as a social tool. Tobacco was introduced to the old world...
, which has been studied more extensively than any other form of consumption.
Tobacco use leads most commonly to diseases affecting the heart and lungs, with smoking being a major risk factor for
heart attacksMyocardial infarction or acute myocardial infarction , commonly known as a heart attack, is the interruption of blood supply to part of the heart, causing some heart cells to die...
,
strokeA stroke is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by thrombosis or embolism or due to a hemorrhage...
s, chronic obstructive pulmonary disease (COPD),
emphysemaEmphysema is a lung disease, characterized by an abnormal, permanent enlargement of air spaces distal to the terminal bronchioles. The disease is coupled with the destruction of walls, but without obvious fibrosis...
, and
cancerCancer is a class of diseases in which a group of cells display uncontrolled growth , invasion , and sometimes metastasis...
(particularly
lung cancerLung cancer is a disease of uncontrolled cell growth in tissues of the lung. This growth may lead to metastasis, which is the invasion of adjacent tissue and infiltration beyond the lungs. The vast majority of primary lung cancers are carcinomas of the lung, derived from epithelial cells...
,
cancers of the larynx and mouthLaryngeal cancer may also be called cancer of the larynx or laryngeal carcinoma. Most laryngeal cancers are squamous cell carcinomas, reflecting their origin from the squamous cells which form the majority of the laryngeal epithelium....
, and
pancreatic cancerPancreatic cancer is a malignant neoplasm of the pancreas. Each year in the United States, about 42,470 individuals are diagnosed with this condition and 35,240 die from the disease. The prognosis is generally poor; less than 5 percent of those diagnosed are still alive five years after diagnosis...
).
The
World Health OrganizationThe World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health...
estimate that tobacco caused 5.4 million deaths in 2004 and 100 million deaths over the course of the 20th century. Similarly, the United States
Centers for Disease Control and PreventionThe Centers for Disease Control and Prevention is a United States federal agency under the Department of Health and Human Services based in Atlanta, Georgia. It works to protect public health and safety by providing information to enhance health decisions, and it promotes health through...
describes tobacco use as "the single most important preventable risk to human health in developed countries and an important cause of premature death worldwide."
Smoke contains several carcinogenic pyrolytic products that bind to DNA and cause many genetic mutations. There are over 19 known chemical carcinogens in cigarette smoke. Tobacco also contains
nicotineNicotine is an alkaloid found in the nightshade family of plants which constitutes approximately 0.6–3.0% of dry weight of tobacco, with biosynthesis taking place in the roots, and accumulating in the leaves...
, which is a highly addictive psychoactive chemical. When tobacco is smoked, nicotine causes physical and psychological dependency. Tobacco use is a significant factor in miscarriages among pregnant smokers, it contributes to a number of other threats to the health of the fetus such as premature births and low birth weight and increases by 1.4 to 3 times the chance for Sudden Infant Death Syndrome (SIDS). The result of scientific studies done in neonatal rats seems to indicate that exposure to cigarette smoke in the womb may reduce the fetal brain's ability to recognize
hypoxicHypoxia is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...
conditions, thus increasing the chance of accidental
asphyxiaAsphyxia is a condition of severely deficient supply of oxygen to the body that arises from being unable to breathe normally. An example of asphyxia is choking...
tion. Incidence of impotence is approximately 85 percent higher in male smokers compared to non-smokers, and it is a key cause of erectile dysfunction (ED).
Prevalence
While a more general measure of the
usage of tobaccoAfter tobacco has been processed, it is used to produce a number of different products.- Chewing tobacco :Chewing is one of the oldest ways of consuming tobacco leaves. Native Americans in both North and South America chewed the leaves of the plant, frequently mixed with lime. Modern chewing...
(both smoked and smokeless) would be more ideal, the
World Health OrganizationThe World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health...
(WHO) reports "data limitations restrict the present indicator to smoked tobacco". Smoking has therefore been studied more extensively than any other form of consumption.
As of 2000, smoking is practiced by 1.22 billion people. Assuming no change in prevalence it is predicted that 1.45 billion people will smoke in 2010 and 1.5 to 1.9 billion in 2025. Assuming that prevalence will decrease at 1% a year and that there will be a modest increase of income of 2%, it is predicted the number of smokers will stand at 1.3 billion in 2010 and 2025.
Smoking is generally five times higher among men than women, however the gender gap declines with younger age. In developed countries smoking rates for men have peaked and have begun to decline, however for women they continue to climb.
As of 2002, about twenty percent of young teens (13–15) smoke worldwide. From which 80,000 to 100,000 children begin smoking every day—roughly half of which live in Asia. Half of those who begin smoking in adolescent years are projected to go on to smoke for 15 to 20 years.
The
World Health OrganizationThe World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health...
(WHO) states that "Much of the disease burden and premature mortality attributable to tobacco use disproportionately affect the poor". Of the 1.22 billion smokers, 1 billion of them live in developing or transitional economies. Rates of smoking have leveled off or declined in the developed world. In the developing world, however, tobacco consumption is rising by 3.4% per year as of 2002.
The WHO in 2004 projected 58.8 million deaths to occur globally, from which 5.4 million are tobacco-attributed, and 4.9 million as of 2007. As of 2002, 70% of the deaths are in developing countries.
Studies
In 1938 a study by a John Hopkins University scientist suggested a strongly negative correlation between smoking and lifespan. In 1950 five studies were published in which "smoking was powerfully implicated in the causation of lung cancer". These included the now classic paper "Smoking and Carcinoma of the Lung" which appeared in the
British Medical JournalBMJ is a partially open access medical journal. It is among the most influential and widely read peer-reviewed general academic journals in the field of medicine in the world....
. This paper reported that "heavy smokers were fifty times as likely as non-smokers to contract lung cancer".
A team of British scientists headed by
Richard DollSir William Richard Shaboe Doll CH OBE FRS was a British physiologist who became the foremost epidemiologist of the 20th century, turning the subject into a rigorous science. He was a pioneer in research linking smoking to health problems...
carried out a longitudinal study of 34,439 medical specialists from 1951 to 2001, generally called the "
British doctors studyThe British doctors study is the generally accepted name of a prospective cohort study which has been running from 1951 to 2001, and in 1956 provided convincing statistical proof that tobacco smoking increased the risk of lung cancer.-Context:...
." The study demonstrated that smoking decreased life expectancy by up to 10 years and that almost half of the smokers died from diseases possibly caused by smoking (cancer, heart disease, and stroke).
After a ban on smoking in all enclosed public places was introduced in Scotland in March 2006, there was a 17 percent reduction in hospital admissions for acute coronary syndrome. 67% of the decrease occurred in non-smokers.
The health effects of tobacco have been significant for the development of the science of
epidemiologyEpidemiology is the study of factors affecting the health and illness of populations, and serves as the foundation and logic of interventions made in the interest of public health and preventive medicine...
. As the mechanism of carcinogenicity is radiomimetic or radiological, the effects are
stochasticStochastic means random.A stochastic process is one whose behavior is non-deterministic in that a system's subsequent state is determined both by the process's predictable actions and by a random element....
. Definite statements may be made only on probabilities of contracting disease. When considered philosophically and theoretically, it is — in principle — impossible to prove a direct causative link between exposure to a radiomimetic poison such as tobacco smoke and the cancer that follows. Tobacco companies have capitalized on this philosophical objection and exploited the doubts of clinicians, who consider only individual cases, on the causal link in the stochastic expression of the toxicity as actual disease.
There have been multiple court cases on the issue that tobacco companies have researched the health effects of tobacco, but suppressed the findings or formatted them to imply lessened or no hazard.
A study published in the journal Pediatrics refers to the danger posed by what the authors call "third-hand smoke" — toxic substances that remain in areas where smoking has recently occurred. The study was
reviewed in an story broadcast by the
Voice of AmericaVoice of America is the official external radio and television broadcasting service of the United States federal government. Its oversight entity is the Broadcasting Board of Governors . VOA provides a wide range of programming for broadcast on radio, TV and the Internet around the world in...
.
Chemical carcinogens
Smoke, or any partially burnt organic matter, is
carcinogenA carcinogen is any substance, radionuclide or radiation that is an agent directly involved in the promotion of cancer or in the increase of its propagation. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...
ic (cancer-causing). The damage a continuing smoker does to their lungs can take up to 20 years before its physical manifestation in lung cancer. Women began smoking later than men, so the rise in death rate amongst women did not appear until later. The male lung cancer death rate decreased in 1975 — roughly 20 years after the fall in cigarette consumption in men. A fall in consumption in women also began in 1975 but by 1991 had not manifested in a decrease in lung cancer related mortalities amongst women.
Smoke contains several carcinogenic
pyrolyticPyrolysis is the chemical decomposition of condensed organic substances by heating. The word is coined from the Greek-derived elements pyro "fire" and lysys "decomposition"....
products that bind to
DNADeoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. The main role of DNA molecules is the long-term storage of information...
and cause genetic mutations. Particularly potent carcinogens are polynuclear aromatic hydrocarbons (PAH), which are
toxicatedToxication is the process of metabolism in which the metabolite of a compound is more toxic than the parent drug or chemical.Toxication may involve:
- Changing the physicochemical properties to cause a change in the microenvironment
...
to mutagenic
epoxideAn epoxide is a cyclic ether with three ring atoms. This ring approximately defines an equilateral triangle, which makes it highly strained. The strained ring makes epoxides more reactive than other ethers. Simple epoxides are named from the parent compound ethylene oxide or oxirane, such as in...
s. The first PAH to be identified as a carcinogen in tobacco smoke was
benzopyreneBenzo[a]pyrene, C20H12, is a five-ring polycyclic aromatic hydrocarbon that is mutagenic and highly carcinogenic. It belongs to a class of polycyclic aromatic compounds known as benzopyrenes, which consist of a benzene ring fused to a pyrene molecule. Benzo[a]pyrene is a...
, which has been shown to toxicate into an epoxide that irreversibly attaches to a cell's nuclear DNA, which may either kill the cell or cause a genetic mutation. If the mutation inhibits
programmed cell deathProgrammed cell-death is death of a cell in any form, mediated by an intracellular program. In contrast to necrosis, which is a form of cell-death that results from acute tissue injury and provokes an inflammatory response, PCD is carried out in a regulated process which generally confers...
, the cell can survive to become a
cancer cellCancer Cell is the first Cell Press journal to focus on a specific disease field, with an editorial scope spanning from basic to clinical-oriented researches and a strong emphasis on translational research...
. Similarly,
acroleinAcrolein is the simplest unsaturated aldehyde. It is produced widely but is most often immediately reacted with other products due to its instability and toxicity. It has a piercing, disagreeable, acrid smell similar to that of burning fat.-Synthesis:Acrolein is prepared industrially by oxidation...
, which is abundant in tobacco smoke, also irreversibly binds to DNA, causes mutations and thus also cancer. However, it needs no activation to become carcinogenic.
There are over 19 known carcinogens in cigarette smoke. The following are some of the most potent carcinogens:
- Polynuclear aromatic hydrocarbons
Polycyclic aromatic hydrocarbons are chemical compounds that consist of fused aromatic rings and do not contain heteroatoms or carry substituents. PAHs occur in oil, coal, and tar deposits, and are produced as byproducts of fuel burning...
are tarTar is the common name for the resinous partially combusted particulate matter produced by the burning of tobacco and other plant material in the act of smoking. Tar is purportedly the most destructive component in habitual tobacco smoking, accumulating in the smoker's lungs over time and damaging...
components produced by pyrolysisPyrolysis is the chemical decomposition of condensed organic substances by heating. The word is coined from the Greek-derived elements pyro "fire" and lysys "decomposition"....
in smoldering organic matter and emitted into smoke. Many of them are highly carcinogenic and mutagenic, because they are toxicatedToxication is the process of metabolism in which the metabolite of a compound is more toxic than the parent drug or chemical.Toxication may involve:
- Changing the physicochemical properties to cause a change in the microenvironment
...
to mutagenic epoxideAn epoxide is a cyclic ether with three ring atoms. This ring approximately defines an equilateral triangle, which makes it highly strained. The strained ring makes epoxides more reactive than other ethers. Simple epoxides are named from the parent compound ethylene oxide or oxirane, such as in...
s, which are electrophilic alkylating agents. The first PAH to be identified as a carcinogen in tobacco smoke was benzopyreneBenzo[a]pyrene, C20H12, is a five-ring polycyclic aromatic hydrocarbon that is mutagenic and highly carcinogenic. It belongs to a class of polycyclic aromatic compounds known as benzopyrenes, which consist of a benzene ring fused to a pyrene molecule. Benzo[a]pyrene is a...
, which been shown to toxicate into a diol epoxide and then permanently attach to nuclear DNA, which may either kill the cell or cause a genetic mutation. The DNA contains the information on how the cell function; in practice, it contains the recipes for protein synthesis. If the mutation inhibits programmed cell deathProgrammed cell-death is death of a cell in any form, mediated by an intracellular program. In contrast to necrosis, which is a form of cell-death that results from acute tissue injury and provokes an inflammatory response, PCD is carried out in a regulated process which generally confers...
, the cell can survive to become a cancer cellCancer Cell is the first Cell Press journal to focus on a specific disease field, with an editorial scope spanning from basic to clinical-oriented researches and a strong emphasis on translational research...
, a cell that does not function like a normal cell. The carcinogenity is radiomimetic, i.e. similar to that produced by ionizing nuclear radiation. Tobacco manufacturers have experimented with combustionless vaporizerA vaporizer is a device used to extract and deliver via inhalation the active ingredients of plant material, commonly cannabis, tobacco, or any of many other herbs or blends . Vaporization is an alternative to smoking...
technology to allow cigarettes to be consumed without the formation of carcinogenic benzopyrenes. However, such products have not become popular.
- Acrolein
Acrolein is the simplest unsaturated aldehyde. It is produced widely but is most often immediately reacted with other products due to its instability and toxicity. It has a piercing, disagreeable, acrid smell similar to that of burning fat.-Synthesis:Acrolein is prepared industrially by oxidation...
is a pyrolysis product that is abundant in cigarette smoke. It gives smoke an acrid smell and an irritating, lachromatory effect and is a major contributor to its carcinogenity. Like PAH metabolites, acrolein is also an electrophilic alkylating agent and permanently binds to the DNA base guanineGuanine is one of the five main nucleobases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, thymine, and uracil. In DNA, guanine is paired with cytosine. With the formula C
5H
5N
5O, guanine is a derivative of purine, consisting of a fused...
, by a conjugate addition followed by cyclization into a hemiaminalA hemiaminal is a functional group or type of chemical compound that has a hydroxyl group and an amine attached to the same carbon atom: -C-. R can be hydrogen or an alkyl group...
. The acrolein-guanine adduct induces mutations during DNA copying and thus causes cancers in a manner similar to PAHs. However, acrolein is 1000 times more abundant than PAHs in cigarette smoke, and is able to react as is, without metabolic activation. Acrolein has been shown to be a mutagenIn biology, a mutagen is a physical or chemical agent that changes the genetic material of an organism and thus increases the frequency of mutations above the natural background level. As many mutations cause cancer, mutagens are typically also carcinogens...
and carcinogenA carcinogen is any substance, radionuclide or radiation that is an agent directly involved in the promotion of cancer or in the increase of its propagation. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...
in human cells. The carcinogenity of acrolein has been difficult to study by animal experimentation, because it has such a toxicity that it tends to kill the animals before they develop cancer. Generally, compounds able to react by conjugate addition as electrophileIn chemistry, an electrophile is a reagent attracted to electrons that participates in a chemical reaction by accepting an electron pair in order to bond to a nucleophile. Because electrophiles accept electrons, they are Lewis acids...
s (so-called Michael acceptors after Michael reactionThe Michael reaction or Michael addition is the nucleophilic addition of a carbanion to an alpha, beta unsaturated carbonyl compound. It belongs to the larger class of conjugate additions. This is one of the most useful methods for the mild formation of C-C bonds...
) are toxic and carcinogenic, because they can permanently alkylate DNA, similarly to mustard gas or aflatoxinAflatoxins are naturally occurring mycotoxins that are produced by many species of Aspergillus, a fungus, most notably Aspergillus flavus and Aspergillus parasiticus. Aflatoxins are toxic and among the most carcinogenic substances known...
. Acrolein is only one of them present in cigarette smoke; for example, crotonaldehydeCrotonaldehyde is a chemical compound with the formula CH3CH=CHCHO. The compound is usually sold as a mixture of the E- and Z-isomers, which differ with respect to the relative position of the methyl and formyl groups. The E-isomer is more common...
has been found in cigarette smoke. Michael acceptors also contribute to the chronic inflammation present in tobacco disease.
- Nitrosamine
Nitrosamines are chemical compounds of the chemical structure R
1N-N=O, some of which are carcinogenic.- Food :...
s are a group of carcinogenic compounds found in cigarette smoke but not in uncured tobacco leaves. Nitrosamines form on flue-cured tobacco leaves during the curing process through a chemical reactionA chemical reaction is a process that leads to the transformation of one set of chemical substances to another. They are studied by chemists under a field of science called chemistry. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, often coming about...
between nicotine and other compounds contained in the uncured leaf and various oxides of nitrogen found in all combustion gases. Switching to indirect-fireIndirect fire means aiming and firing a gun without relying on a direct line of sight between the gun and its target, as in the case of direct fire...
curing has been shown to reduce nitrosamine levels to less than 0.1 parts per million.
Radioactive carcinogens
In addition to chemical, nonradioactive carcinogens, tobacco and tobacco smoke contain small amounts of lead-210 (
210Pb) and polonium-210 (
210Po) both of which are radioactive carcinogens. The presence of polonium-210 in mainstream cigarette smoke has been experimentally measured at levels of 0.0263–0.036 pCi (0.97–1.33 mBq), which is equivalent to about 0.1 pCi per milligram of smoke (4 mBq/mg); or about 0.81 pCi of lead 210 per gram of dry condensed smoke (30 Bq/kg).
Research by NCAR
radiochemistRadiochemistry is the chemistry of radioactive materials, where radioactive isotopes of elements are used to study the properties and chemical reactions of non-radioactive isotopes...
Ed Martell determined that radioactive compounds in cigarette smoke are deposited in "hot spots" where bronchial tubes branch. Since tar from cigarette smoke is resistant to dissolving in lung fluid, the radioactive compounds have a great deal of time to undergo
radioactive decayRadioactive decay is the process in which an unstable atomic nucleus spontaneously loses energy by emitting ionizing particles and radiation. This decay, or loss of energy, results in an atom of one type, called the parent nuclide transforming to an atom of a different type, named the daughter...
before being cleared by natural processes. Indoors, these radioactive compounds linger in secondhand smoke, and therefore greater exposure occurs when these radioactive compounds are inhaled during normal breathing, which is deeper and longer than when inhaling cigarettes. Damage to the protective epithelial tissue from smoking only increases the prolonged retention of insoluble polonium 210 compounds produced from burning tobacco. Martell estimated that a carcinogenic radiation dose of 80-100 rads is delivered the lung tissue of most smokers who die of lung cancer.
The view that polonium 210 is responsible for many cases of cancer in tobacco smokers is disputed by at least one researcher.
Nicotine
NicotineNicotine is an alkaloid found in the nightshade family of plants which constitutes approximately 0.6–3.0% of dry weight of tobacco, with biosynthesis taking place in the roots, and accumulating in the leaves...
that is contained in cigarettes and other smoked tobacco products is a
stimulantStimulants, also sometimes called psychostimulants, are psychoactive drugs which induce temporary improvements in either mental or physical function or both. Examples of these kinds of effects may include enhanced alertness, wakefulness, and locomotion, among others...
and is one of the main factors leading to continued tobacco smoking. Although the amount of nicotine inhaled with tobacco smoke is quite small (most of the substance is destroyed by the heat) it is still sufficient to cause physical and/or psychological dependence. The amount of nicotine absorbed by the body from smoking depends on many factors, including the type of tobacco, whether the smoke is inhaled, and whether a filter is used. Despite the design of various cigarettes advertised and even tested on machines to deliver less of the toxic tar, studies show that when smoked by humans instead of machines, they deliver the same net amount of smoke. Ingesting a compound by smoking is one of the most rapid and efficient methods of introducing it into the bloodstream, second only to injection, which allows for the rapid feedback which supports the smokers' ability to
titrateTitration is a common laboratory method of quantitative chemical analysis that is used to determine the unknown concentration of a known reactant...
their dosage. On average it takes about ten seconds for the substance to reach the brain. As a result of the efficiency of this delivery system, many smokers feel as though they are unable to cease. Of those who attempt cessation and last three months without succumbing to nicotine, most are able to remain smoke free for the rest of their lives. There exists a possibility of depression in some who attempt cessation, as with other psychoactive substances. Depression is also common in teenage smokers; teens who smoke are four times as likely to develop depressive symptoms as their nonsmoking peers.
Although nicotine does play a role in acute episodes of some diseases (including
strokeA stroke is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by thrombosis or embolism or due to a hemorrhage...
, impotence, and
heart diseaseHeart disease or cardiopathy is an umbrella term for a variety for different diseases affecting the heart. As of 2007, it is the leading cause of death in the United States, England, Canada and Wales, killing one person every 34 seconds in the United States alone.-Coronary heart disease:Coronary...
) by its stimulation of adrenaline release, which raises
blood pressureBlood pressure is the pressure exerted by circulating blood on the walls of blood vessels, and is one of the principal vital signs. During each heartbeat, BP varies between a maximum and a minimum pressure...
,
heart rateHeart rate is determined by the number of heartbeats per unit of time, typically expressed as beats per minute , it can vary with as the body's need for oxygen changes, such as during exercise or sleep. The measurement of heart rate is used by medical professionals to assist in the diagnosis and...
, and free fatty acids, the most serious longer term effects are more the result of the products of the smouldering combustion process. This has enabled development of various nicotine delivery systems, such as the
nicotine patchA nicotine patch is a transdermal patch that releases nicotine into the body through the skin. It is usually used as a method to quit smoking. The first patch appeared in 1993.-Cost:...
or
nicotine gumNicotine gum is a type of chewing gum that delivers nicotine to the body. It is used as an aid in smoking cessation and in quitting smokeless tobacco. The nicotine is delivered to the bloodstream via absorption by the tissues of the mouth....
, that can satisfy the addictive craving by delivering nicotine without the harmful combustion by-products. This can help the heavily dependent smoker to quit gradually, while discontinuing further damage to health.
NicotineNicotine is an alkaloid found in the nightshade family of plants which constitutes approximately 0.6–3.0% of dry weight of tobacco, with biosynthesis taking place in the roots, and accumulating in the leaves...
is a highly addictive psychoactive chemical. When tobacco is smoked, most of the nicotine is
pyrolyzedPyrolysis is the chemical decomposition of condensed organic substances by heating. The word is coined from the Greek-derived elements pyro "fire" and lysys "decomposition"....
; a dose sufficient to cause mild somatic dependency and mild to strong psychological dependency remains. There is also a formation of harmane (a MAO inhibitor) from the acetaldehyde in cigarette smoke, which seems to play an important role in nicotine addiction probably by facilitating dopamine release in the nucleus accumbens in response to nicotine stimuli. According to studies by Henningfield and Benowitz, overall nicotine is more addictive than
cannabisCannabisalso known as marijuana or marihuana, and ganja , among many other namesrefers to any number of preparations of the Cannabis plant intended for use as a psychoactive drug...
,
caffeineCaffeine is a bitter, white crystalline xanthine alkaloid that is a psychoactive stimulant drug. Caffeine was discovered by a German chemist, Friedrich Ferdinand Runge, in 1819. He coined the term kaffein, a chemical compound in coffee, which in English became caffeine...
,
ethanolEthanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug, best known as the type of alcohol found in alcoholic beverages and in modern thermometers. Ethanol is one of the oldest recreational drugs...
,
cocaineCocaine is a crystalline tropane alkaloid that is obtained from the leaves of the coca plant. The name comes from "coca" in addition to the alkaloid suffix -ine, forming cocaine. It is a stimulant of the central nervous system and an appetite suppressant...
, and
heroinHeroin, or diacetylmorphine , also known as diamorphine , is a semi-synthetic opioid drug synthesized from morphine, a derivative of the opium poppy. It is the 3,6-diacetyl ester of morphine...
when considering both somatic and psychological dependence. However, due to the stronger withdrawal effects of
ethanolEthanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug, best known as the type of alcohol found in alcoholic beverages and in modern thermometers. Ethanol is one of the oldest recreational drugs...
,
cocaineCocaine is a crystalline tropane alkaloid that is obtained from the leaves of the coca plant. The name comes from "coca" in addition to the alkaloid suffix -ine, forming cocaine. It is a stimulant of the central nervous system and an appetite suppressant...
and
heroinHeroin, or diacetylmorphine , also known as diamorphine , is a semi-synthetic opioid drug synthesized from morphine, a derivative of the opium poppy. It is the 3,6-diacetyl ester of morphine...
, nicotine may have a lower potential for somatic dependence than these substances. A study by Perrine concludes that nicotine's potential for psychological dependency exceeds all other studied drugs - even ethanol, an extremely physically addictive substance with severe
withdrawalDelirium tremens is an acute episode of delirium that is usually caused by withdrawal from alcohol, first described in 1813...
symptoms that can be fatal. About half of Canadians who currently smoke have tried to quit.
McGill UniversityMcGill University is a public research university located in Montreal, Quebec, Canada. It bears the name of James McGill, a prominent Montreal merchant from Scotland, whose bequest formed the beginning of the university...
health professor Jennifer O'Loughlin stated that nicotine addiction can occur as soon as five months after the start of smoking.
Recent evidence has shown that smoking tobacco increases the release of
dopamineDopamine is a neurotransmitter occurring in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this phenethylamine functions as a neurotransmitter, activating the five types of dopamine receptors — D
1, D
2, D
3, D
4, and...
in the brain, specifically in the mesolimbic pathway, the same neuro-reward circuit activated by drugs of abuse such as
heroinHeroin, or diacetylmorphine , also known as diamorphine , is a semi-synthetic opioid drug synthesized from morphine, a derivative of the opium poppy. It is the 3,6-diacetyl ester of morphine...
and
cocaineCocaine is a crystalline tropane alkaloid that is obtained from the leaves of the coca plant. The name comes from "coca" in addition to the alkaloid suffix -ine, forming cocaine. It is a stimulant of the central nervous system and an appetite suppressant...
. This suggests nicotine use has a pleasurable effect that triggers positive reinforcement. One study found that smokers exhibit better reaction-time and memory performance compared to non-smokers, which is consistent with increased activation of dopamine receptors. Neurologically, rodent studies have found that nicotine self-administration causes lowering of reward thresholds—a finding opposite that of most other drugs of abuse (e.g. cocaine and heroin). This increase in reward circuit sensitivity persisted months after the self-administration ended, suggesting that nicotine's alteration of brain reward function is either long lasting or permanent. Furthermore, it has been found that nicotine can activate long term potentiation
in vivo and
in vitro. These studies suggests nicotine’s "trace memory" may contribute to difficulties in nicotine abstinence.
The carcinogenity of tobacco smoke is not explained by
nicotineNicotine is an alkaloid found in the nightshade family of plants which constitutes approximately 0.6–3.0% of dry weight of tobacco, with biosynthesis taking place in the roots, and accumulating in the leaves...
per se, which is not carcinogenic or mutagenic. However, it inhibits
apoptosisApoptosis is the process of programmed cell death that may occur in multicellular organisms. Programmed cell death involves a series of biochemical events leading to a characteristic cell morphology and death; in more specific terms, a series of biochemical events that lead to a variety of...
, therefore accelerating existing cancers. Also,
NNK4-- 1--1-butanone is a nitrosamine present in tobacco that is a potent procarcinogen. It is activated by CYP2A6. It is a biomarker of exposure to cigarette smoke. It is produced upon the curing of tobacco....
, a nicotine derivative converted from nicotine, can be carcinogenic.
It is worth noting that
nicotineNicotine is an alkaloid found in the nightshade family of plants which constitutes approximately 0.6–3.0% of dry weight of tobacco, with biosynthesis taking place in the roots, and accumulating in the leaves...
, although frequently implicated in producing
tobaccoTobacco is an agricultural product processed from the leaves of plants in the genus Nicotiana. It can be consumed, used as an organic pesticide, and in the form of nicotine tartrate it is used in some medicines. In consumption it most commonly appears in the forms of smoking, chewing, snuffing, or...
addiction, is not significantly addictive when administered alone. The addictive potential manifests itself after co-administration of an MAOI inhibitor, which specifically causes
sensitizationSensitization is an example of non-associative learning in which the progressive amplification of a response follows repeated administrations of a stimulus. An everyday example of this mechanism is the repeated tonic stimulation of peripheral nerves that will occur if a person rubs his arm...
of the locomotor response in rats, a measure of addictive potential.
Genetic
According to three separate studies commissioned by governments in the US and Europe, scientists have identified a genetic link that makes people more likely to become addicted to tobacco. This genetic variation causes individuals to smoke more cigarettes, makes it harder for them to quit and increases their likelihood of developing lung cancer by up to 80%.
Genetic markers of more than 35,000 people (mostly smokers and ex-smokers) were surveyed by scientists in three separate studies, and all three found lung cancer to be associated with similar sets of genetic differences. The genetic variations of note encode nicotine receptors on cells and were identified on a region of chromosome 15. Possessing a single copy of the mutation raises an individual's risk of lung cancer by approximately 30%; for two copies the increase is about 80%. The gene was found to be attributable to 14% of lung cancer cases, and it was found to confer similar lung cancer risks irrespective of smoking status or quantity smoked.
Another study related to genetic changes in smokers was conducted by Wan L Lam and Stephen Lam from the BC Cancer Agency, in 2007. The study revealed that cigarette smoke can turn on or off some of the genes, which otherwise would remain inactive. Some changes on genetic level could be reversed after the smoking was quit, yet others could not. Examples of reversible genes involved the so-called xenofobic functions, nucleotide metabolism and mucus secretion. Smoking turns off some DNA repair genes that cannot be reversed. It also switches off permanently some genes responsible from protection from cancer growth in the body.
Health effects
Most scientists involved in cancer research believe that the environmental factors, which include anything the people interact with such as lifestyle choices, their diet, natural and medical radiation, sunlight exposure, workplace exposure, and socioeconomic factors that affect exposures and susceptibility—may be a major contributor to the development of cancer. Other factors that play a major role in cancer development are infectious diseases, aging, and individual susceptibility such as genetic predisposition. Because of these confounding variables, it is difficult to distinguish which factor or condition contributes to the development of cancer. For example, smoking tobacco is known to cause cancer in humans, but not all people who smoke develop smoking-related cancer; however, with some substances or exposure circumstances, cancer may develop after even brief exposure.
A person's increased risk of contracting disease is directly proportional to the length of time that a person continues to smoke as well as the amount smoked. However, if someone stops smoking, then these chances gradually decrease as the damage to their body is repaired. A year after quitting, the risk of contracting heart disease is half that of a continuing smoker. The health risks of smoking are not uniform across all smokers. Risks vary according to amount of tobacco smoked, with those who smoke more at greater risk. Light smoking is still a health risk. Likewise, smoking "light" cigarettes does not reduce the risks.
Tobacco use most commonly leads to diseases affecting the heart and
lungsThe respiratory systems function is to allow gas exchange to all parts of the body. The space between the alveoli & the capillaries, the anatomy or structure of the exchange system, and the precise physiological uses of the exchanged gases vary depending on the organism...
, with smoking being a major risk factor for
heart attacksMyocardial infarction or acute myocardial infarction , commonly known as a heart attack, is the interruption of blood supply to part of the heart, causing some heart cells to die...
, Chronic Obstructive Pulmonary Disease (COPD),
emphysemaEmphysema is a lung disease, characterized by an abnormal, permanent enlargement of air spaces distal to the terminal bronchioles. The disease is coupled with the destruction of walls, but without obvious fibrosis...
, and
cancerCancer is a class of diseases in which a group of cells display uncontrolled growth , invasion , and sometimes metastasis...
, particularly
lung cancerLung cancer is a disease of uncontrolled cell growth in tissues of the lung. This growth may lead to metastasis, which is the invasion of adjacent tissue and infiltration beyond the lungs. The vast majority of primary lung cancers are carcinomas of the lung, derived from epithelial cells...
, cancers of the
larynxThe larynx , colloquially known as the voicebox, is an organ in the neck of mammals involved in protection of the trachea and sound production...
and
mouthThe mouth, buccal cavity, or oral cavity is the first portion of the alimentary canal that receives food and begins digestion by mechanically breaking up the solid food particles into smaller pieces and mixing them with saliva...
, and
pancreatic cancerPancreatic cancer is a malignant neoplasm of the pancreas. Each year in the United States, about 42,470 individuals are diagnosed with this condition and 35,240 die from the disease. The prognosis is generally poor; less than 5 percent of those diagnosed are still alive five years after diagnosis...
. Overall life expectancy is also reduced in regular smokers, with estimates ranging from 2.5 to 10 years fewer than nonsmokers. About half of male smokers will die of illness due to smoking. The association of smoking with lung cancer is strongest, both in the public perception and etiologically. People who have smoked tobacco at some point have about a one in ten chance of developing lung cancer during their lifetime. If one looks at men who continue to smoke tobacco, the risk increases to one in six. Historically, lung cancer was considered to be a rare disease prior to
World War IWorld War I , also known as the First World War, the Great War, and the War to End All Wars, was a global military conflict which involved most of the world's great powers, assembled in two opposing alliances: the Triple Entente and the Triple Alliance...
and was perceived as something most physicians would never see during their career. With the postwar rise in popularity of cigarette smoking came a virtual epidemic of lung cancer.
A person's increased risk of contracting disease is directly proportional to the length of time that a person smokes, as well as to the amount smoked, and doctors use the approximation "pack years" in assessing the likelihood of smoking-related illness. However, if someone stops smoking, then their risk declines over time, and the reduction in their lung function will stop.
Mortality
Male and female smokers lose an average of 13.2 and 14.5 years of life, respectively.
According to the results of a 50 year study of 34,439 male British doctors, at least half of all lifelong smokers die earlier as a result of smoking.
In the United States, cigarette smoking and exposure to tobacco smoke results in at least 443,000 premature deaths annually.
Cancer
The primary risks of tobacco usage include many forms of cancer, particularly
lung cancerLung cancer is a disease of uncontrolled cell growth in tissues of the lung. This growth may lead to metastasis, which is the invasion of adjacent tissue and infiltration beyond the lungs. The vast majority of primary lung cancers are carcinomas of the lung, derived from epithelial cells...
,
cancer of the kidneyRenal cell carcinoma is a kidney cancer that originates in the lining of the proximal convoluted tubule, the very small tubes in the kidney that filter the blood and remove waste products. RCC is the most common type of kidney cancer in adults, responsible for approximately 80% of cases...
,
cancer of the larynxLaryngeal cancer may also be called cancer of the larynx or laryngeal carcinoma. Most laryngeal cancers are squamous cell carcinomas, reflecting their origin from the squamous cells which form the majority of the laryngeal epithelium....
and head and neck,
breast cancerBreast cancer is a cancer that starts in the breast, usually in the inner lining of the milk ducts or lobules. There are different types of breast cancer, with different stages , aggressiveness, and genetic makeup. With best treatment, 10-year disease-free survival varies from 98% to 10%...
,
bladderBladder cancer refers to any of several types of malignant growths of the urinary bladder. It is a disease in which abnormal cells multiply without control in the bladder. The bladder is a hollow, muscular organ that stores urine; it is located in the pelvis...
,
esophagusEsophageal cancer is malignancy of the esophagus. There are various subtypes, primarily squamous cell cancer and adenocarcinoma. Squamous cell cancer arises from the cells that line the upper part of the esophagus. Adenocarcinoma arises from glandular cells that are present at the junction of the...
,
pancreasPancreatic cancer is a malignant neoplasm of the pancreas. Each year in the United States, about 42,470 individuals are diagnosed with this condition and 35,240 die from the disease. The prognosis is generally poor; less than 5 percent of those diagnosed are still alive five years after diagnosis...
, and stomach. There is some evidence suggesting an increased risk of
myeloid leukemiaMyeloid leukemia is a type of leukemia affecting myeloid tissue .Types include:* Acute myelogenous leukemia* Chronic myelogenous leukemia...
, squamous cell sinonasal cancer,
liver cancerHepatocellular carcinoma is a primary malignancy of the liver. Most cases of HCC are secondary to either a viral hepatitide infection or cirrhosis...
,
cervical cancerCervical cancer is malignant neoplasm of the cervix uteri or cervical area. It may present with vaginal bleeding but symptoms may be absent until the cancer is in its advanced stages...
,
colorectal cancerColorectal cancer, also called colon cancer or large bowel cancer, includes cancerous growths in the colon, rectum and appendix. With 655,000 deaths worldwide per year, it is the third most common form of cancer and the third leading cause of cancer-related death in the Western world. Many...
after an extended latency, childhood cancers and cancers of the gall bladder,
adrenal glandIn mammals, the adrenal glands are the star-shaped endocrine glands that sit on top of the kidneys; their name indicates that position...
and
small intestineIn vertebrates, the small intestine is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where the vast majority of digestion and absorption of food takes place. In invertebrates such as worms, the terms "gastrointestinal tract" and "large...
.
Lung Cancer
The risk of dying from lung
cancer before age 85 is 22.1% for a male smoker and
11.9% for a female current smoker, in the absence of
competing causes of death. The corresponding estimates for
lifelong nonsmokers are a 1.1% probability of dying from
lung cancer before age 85 for a man of European descent, and
a 0.8% probability for a woman.
Pulmonary
In smoking, long term exposure to compounds found in the smoke such as
carbon monoxideCarbon monoxide is a colorless, odorless and tasteless gas, yet very toxic to humans. It consists of one carbon atom and one oxygen atom, connected by a covalent double bond and a dative covalent bond...
,
cyanideA cyanide is any chemical compound that contains the cyano group , which consists of a carbon atom triple-bonded to a nitrogen atom. Inorganic cyanides are hydrogen cyanide salts in which cyanide is generally the anion CN
-. Organic compounds that have a -C≡N functional group bonded to...
, and so forth—, are believed to be responsible for pulmonary damage and for loss of elasticity in the alveoli, leading to emphysema and COPD. The carcinogen acrolein and its derivatives also contribute to the chronic inflammation present in COPD.
Secondhand smoke is a mixture of smoke from the burning end of a cigarette, pipe or cigar and the smoke exhaled from the lungs of smokers. It is involuntarily inhaled, lingers in the air hours after cigarettes have been extinguished, and can cause a wide range of adverse health effects, including cancer, respiratory infections, and asthma. Nonsmokers who are exposed to secondhand smoke at home or work increase their heart disease risk by 25–30% and their lung cancer risk by 20–30%. Secondhand smoke has been estimated to cause 38,000 deaths per year, of which 3,400 are deaths from lung cancer in non-smokers.
Chronic obstructive pulmonary disease (COPD) caused by smoking, known as tobacco disease, is a permanent, incurable reduction of pulmonary capacity characterized by shortness of breath, wheezing, persistent cough with
sputumSputum is matter that is expectorated from the respiratory tract, such as mucus or phlegm, mixed with saliva, which can then be spat from the mouth. It is usually associated with air passages in diseased lungs, bronchi, or upper respiratory tract...
, and damage to the lungs, including
emphysemaEmphysema is a lung disease, characterized by an abnormal, permanent enlargement of air spaces distal to the terminal bronchioles. The disease is coupled with the destruction of walls, but without obvious fibrosis...
and
chronic bronchitisChronic bronchitis is a chronic inflammation of the bronchi in the lungs. It is generally considered one of the two forms of chronic obstructive pulmonary disease...
.
Influenza
A study of an outbreak of A(H1N1) influenza in an Israeli military unit of 336 healthy young men to determine the relation of cigarette smoking to the incidence of clinically apparent influenza, revealed that, of 168 smokers, 68.5 per cent had influenza, as compared with 47.2 per cent of nonsmokers. Influenza was also more severe in the smokers; 50.6 per cent of the smokers lost work days or required bed rest, or both, as compared with 30.1 per cent of the nonsmokers.
According to a study of 1,900 male cadets after the 1968 Hong Kong A2 influenza epidemic at a South Carolina military academy, compared with nonsmokers heavy smokers (more than 20 cigarettes per day), had 21% more illnesses and 20% more bed rest, light smokers (less than 20 cigarettes per day) had 10% more illnesses and 7% more bed rest.
The effect of cigarette smoking upon epidemic influenza was studied prospectively among 1,811 male college students. Clinical influenza incidence among those who daily smoked 21 or more cigarettes was 21% higher than that of non-smokers. Influenza incidence among smokers of 1 to 20 cigarettes daily was intermediate between non-smokers and heavy cigarette smokers.
Surveillance of a 1979 influenza out-break at a military base for women in Israel revealed that, Influenza symptoms developed in 60.0% of the current smokers vs. 41.6% of the nonsmokers.
Smoking seems to cause a higher relative influenza-risk in older populations than in younger populations. In a prospective study of community-dwelling people 60–90 years of age, during 1993, of unimmunized people 23% of smokers had clinical influenza as compared with 6 % of non-smokers.
Smoking may substantially contribute to the growth of influenza epidemics affecting the entire population. However the proportion of influenza cases in the general non-smoking population attributable to smokers has not yet been calculated.
Cardiovascular
Inhalation of tobacco smoke causes several immediate responses within the heart and blood vessels. Within one minute the heart rate begins to rise, increasing by as much as 30 percent during the first 10 minutes of smoking. Carbon monoxide in tobacco smoke exerts its
negative effectsCarbon monoxide poisoning occurs after enough inhalation of carbon monoxide . Carbon monoxide is a toxic gas, but, being colorless, odorless, tasteless, and non-irritating, it is very difficult for people to detect...
by reducing the blood’s ability to carry oxygen.
Smoking also increases the chance of
heart diseaseHeart disease or cardiopathy is an umbrella term for a variety for different diseases affecting the heart. As of 2007, it is the leading cause of death in the United States, England, Canada and Wales, killing one person every 34 seconds in the United States alone.-Coronary heart disease:Coronary...
,
strokeA stroke is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by thrombosis or embolism or due to a hemorrhage...
,
atherosclerosisAtherosclerosis is the condition in which an artery wall thickens as the result of a build-up of fatty materials such as cholesterol...
, and peripheral vascular disease. Several ingredients of tobacco lead to the narrowing of blood vessels, increasing the likelihood of a blockage, and thus a
heart attackMyocardial infarction or acute myocardial infarction , commonly known as a heart attack, is the interruption of blood supply to part of the heart, causing some heart cells to die...
or
strokeA stroke is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by thrombosis or embolism or due to a hemorrhage...
. According to a study by an international team of researchers, people under 40 are five times more likely to have a heart attack if they smoke.
Latest research of the American biologists have determined that cigarette smoke also influences the process of cell division in the cardiac muscle and changes heart's shape.
The usage of tobacco has also been linked to
Buerger's diseaseBuergers's disease is a recurring inflammation and thrombosis of small and medium arteries and veins of the hands and feet...
(
thromboangiitis obliterans) the acute inflammation and thrombosis (clotting) of arteries and veins of the hands and feet.
The current Surgeon General’s Report concluded that there is no risk-free level of exposure to secondhand smoke. Even short exposures to secondhand smoke can cause blood platelets to become stickier, damage the lining of blood vessels, decrease coronary flow velocity reserves, and reduce heart rate variability, potentially increasing the risk of
heart attackMyocardial infarction or acute myocardial infarction , commonly known as a heart attack, is the interruption of blood supply to part of the heart, causing some heart cells to die...
. New research indicates that private research conducted by cigarette company
Philip MorrisPhilip Morris International is an international tobacco company, with products sold in over 160 countries. In 2007, it held a 15.6% share of the international cigarette market outside of the USA and reported revenues net of excise taxes of $22.8 billion and operating income of $8.9 billion.Until...
in the 1980s showed that secondhand smoke was toxic, yet the company suppressed the finding during the next two decades.
Although cigarette smoking causes a greater increase of the risk of cancer than cigar smoking, cigar smokers still have an increased risk for many health problems, including cancer, when compared to non-smokers. As for Environmental Tobacco Smoke (ETS, or "
Second-hand SmokingPassive smoking is the inhalation of smoke, called secondhand smoke or environmental tobacco smoke , from tobacco products used by others. It occurs when tobacco smoke permeates any environment, causing its inhalation by people within that environment...
"), the NIH study points to the large amount of smoke generated by one cigar, saying "cigars can contribute substantial amounts of tobacco smoke to the indoor environment; and, when large numbers of cigar smokers congregate together in a cigar smoking event, the amount of ETS produced is sufficient to be a health concern for those regularly required to work in those environments."
Smoking tends to increase blood cholesterol levels. Furthermore, the ratio of high-density lipoprotein (the "good" cholesterol) to low-density lipoprotein (the "bad" cholesterol) tends to be lower in smokers compared to non-smokers. Smoking also raises the levels of fibrinogen and increases platelet production (both involved in blood clotting) which makes the blood viscous. Carbon monoxide binds to haemoglobin (the oxygen-carrying component in red blood cells), resulting in a much stabler complex than haemoglobin bound with oxygen or carbon dioxide—the result is permanent loss of blood cell functionality. Blood cells are naturally recycled after a certain period of time, allowing for the creation of new, functional erythrocytes. However, if carbon monoxide exposure reaches a certain point before they can be recycled, hypoxia (and later death) occurs. All these factors make smokers more at risk of developing various forms of arteriosclerosis. As the arteriosclerosis progresses, blood flows less easily through rigid and narrowed blood vessels, making the blood more likely to form a thrombosis (clot). Sudden blockage of a blood vessel may lead to an infarction (e.g. stroke). However, it is also worth noting that the effects of smoking on the heart may be more subtle. These conditions may develop gradually given the smoking-healing cycle (the human body heals itself between periods of smoking), and therefore a smoker may develop less significant disorders such as worsening or maintenance of unpleasant dermatological conditions, e.g. eczema, due to reduced blood supply. Smoking also increases blood pressure and weakens blood vessels.
Oral
Perhaps the most serious oral condition that can arise is that of
oral cancerOral cancer or Oral cavity cancer, a subtype of head and neck cancer, is any cancerous tissue growth located in the oral cavity. It may arise as a primary lesion originating in any of the oral tissues, by metastasis from a distant site of origin, or by extension from a neighboring anatomic...
. However, smoking also increases the risk for various other oral diseases, some almost completely exclusive to tobacco users. The
National Institutes of HealthThe National Institutes of Health is an agency of the United States Department of Health and Human Services and is the primary agency of the United States government responsible for biomedical and health-related research. It consists of 27 separate institutes and centers which includes the Office...
, through the
National Cancer InstituteThe National Cancer Institute is part of the United States Federal government's National Institutes of Health. The NCI is a federally funded research and development center, one of eight agencies that compose the Public Health Service in the United States Department of Health and Human Services. ...
, determined in 1998 that "cigar smoking causes a variety of cancers including cancers of the
oral cavityOral cancer or Oral cavity cancer, a subtype of head and neck cancer, is any cancerous tissue growth located in the oral cavity. It may arise as a primary lesion originating in any of the oral tissues, by metastasis from a distant site of origin, or by extension from a neighboring anatomic...
(lip, tongue, mouth, throat),
esophagusEsophageal cancer is malignancy of the esophagus. There are various subtypes, primarily squamous cell cancer and adenocarcinoma. Squamous cell cancer arises from the cells that line the upper part of the esophagus. Adenocarcinoma arises from glandular cells that are present at the junction of the...
, larynx, and
lungLung cancer is a disease of uncontrolled cell growth in tissues of the lung. This growth may lead to metastasis, which is the invasion of adjacent tissue and infiltration beyond the lungs. The vast majority of primary lung cancers are carcinomas of the lung, derived from epithelial cells...
." Pipe smoking involves significant health risks, particularly oral cancer. Roughly half of periodontitis or inflammation around the teeth cases attributed to current or former smoking. Smokeless tobacco causes gingival recession and white mucosal
lesionA lesion is any abnormal tissue found on or in an organism, usually damaged by disease or trauma. Lesion is derived from the Latin word laesio which means injury.-Causes of lesions:...
s. Up to 90% of periodontitis patients who are not helped by common modes of treatment are smokers. Smokers have significantly greater loss of bone height than nonsmokers, and the trend can be extend to pipe smokers to have more bone loss than nonsmokers. Smoking has been proven to be an important factor in the staining of teeth.
HalitosisHalitosis, or most commonly bad breath are terms used to describe noticeably unpleasant odors exhaled in breathing – whether the smell is from an oral source due to bacteria....
or bad breath is common among tobacco smokers. Tooth loss has been shown to be 2 to 3 times higher in smokers than in non-smokers. In addition, complications may further include
leukoplakiaLeukoplakia is adherent white plaques or patches on the mucous membranes of the oral cavity, including the tongue. The clinical appearance is highly variable. Leukoplakia is not a specific disease entity, but is diagnosis of exclusion...
the adherent white plaques or patches on the mucous membranes of the oral cavity, including the tongue, and a loss of taste sensation or
salivaSaliva is the watery and usually frothy substance produced in the mouths of humans and most other animals. Saliva is produced in and secreted from the salivary glands...
ry changes.
Infection
Tobacco is also linked to susceptibility to infectious diseases, particularly in the lungs. Smoking more than 20
cigaretteA cigarette is a product consumed through smoking and manufactured out of cured and finely cut tobacco leaves and reconstituted tobacco, often combined with other additives, then rolled or stuffed into a paper-wrapped cylinder...
s a day increases the risk of
tuberculosisTuberculosis is a common and often deadly infectious disease caused by mycobacteria...
by two to four times, and being a current smoker has been linked to a fourfold increase in the risk of invasive pneumococcal disease. It is believed that smoking increases the risk of these and other pulmonary and respiratory tract infections both through structural damage and through effects on the immune system. The effects on the immune system include an increase in CD4+ cell production attributable to nicotine, which has tentatively been linked to increased
HIVHuman immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which the immune system begins to fail, leading to life-threatening opportunistic infections. Infection with HIV occurs by the transfer of blood, semen, vaginal fluid,...
susceptibility. The usage of tobacco also increases rates of infection:
common coldAcute viral rhinopharyngitis, or acute coryza, known as an upper respiratory virus, or commonly called a cold, is a contagious, viral infectious disease of the upper respiratory system, primarily caused by rhinoviruses, or coronaviruses...
and
bronchitisAcute bronchitis is an inflammation of the large bronchi in the lungs that is usually caused by viruses or bacteria and may last several days or weeks. Characteristic symptoms include cough, sputum production, and shortness of breath and wheezing related to the obstruction of the inflamed airways...
, chronic obstructive pulmonary disease,
emphysemaEmphysema is a lung disease, characterized by an abnormal, permanent enlargement of air spaces distal to the terminal bronchioles. The disease is coupled with the destruction of walls, but without obvious fibrosis...
and
chronic bronchitisChronic bronchitis is a chronic inflammation of the bronchi in the lungs. It is generally considered one of the two forms of chronic obstructive pulmonary disease...
in particular.
Smoking reduces the risk of
Kaposi's sarcomaKaposi's sarcoma is a tumor caused by Human herpesvirus 8 , also known as Kaposi's sarcoma-associated herpesvirus . It was originally described by Moritz Kaposi, a Hungarian dermatologist practicing at the University of Vienna in 1872. It became more widely known as one of the AIDS defining...
in people without
HIV infectionHuman immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which the immune system begins to fail, leading to life-threatening opportunistic infections. Infection with HIV occurs by the transfer of blood, semen, vaginal fluid,...
.
Psychological
Smokers report a variety of physical and psychological effects from smoking tobacco. Those new to smoking may experience
nauseaNausea is the sensation of unease and discomfort in the stomach with an urge to vomit.-Causes:...
,
dizzinessDizziness refers to an impairment in spatial perception and stability. It is considered imprecise. It can be used to mean vertigo, presyncope, disequilibrium, or for a non-specific feeling such as giddiness or foolishness....
, and
rapid heart beatTachycardia comes from the Greek words tachys and kardia . Tachycardia typically refers to a heart rate that exceeds the normal range for a resting heartrate...
. The unpleasant symptoms will eventually vanish over time, with repeated use, as the body builds a tolerance to the chemicals in the cigarettes, such as nicotine. The usage of tobacco also creates cognitive dysfunction, which include: increased risk (or decrease) of Alzheimer's disease and decline in cognitive abilities, reduced memory and cognitive abilities in adolescent smokers, brain shrinkage (cerebral atrophy)
In many respects,
nicotineNicotine is an alkaloid found in the nightshade family of plants which constitutes approximately 0.6–3.0% of dry weight of tobacco, with biosynthesis taking place in the roots, and accumulating in the leaves...
acts on the nervous system in a similar way to
caffeineCaffeine is a bitter, white crystalline xanthine alkaloid that is a psychoactive stimulant drug. Caffeine was discovered by a German chemist, Friedrich Ferdinand Runge, in 1819. He coined the term kaffein, a chemical compound in coffee, which in English became caffeine...
. Some writings have stated that smoking can also increase mental
concentrationIn chemistry, concentration is the measure of how much of a given substance there is mixed with another substance. This can apply to any sort of chemical mixture, but most frequently the concept is limited to homogeneous solutions, where it refers to the amount of solute in the solvent.To...
; one study documents a significantly better IQ on the normed Advanced Raven Progressive Matrices test after smoking. Most smokers say they enjoy smoking, which is part of the reason why many continue to do so even though they are aware of the health risks. Taste, smell, and visual enjoyment are also major contributions to the enjoyment of smoking, in addition to camaraderie with other smokers. Ironically, chronic exposure to tobacco smoke may inhibit one's sense of taste and smell, rendering him or her less able to enjoy these aspects of tobacco smoking.
Most smokers, when denied access to
nicotineNicotine is an alkaloid found in the nightshade family of plants which constitutes approximately 0.6–3.0% of dry weight of tobacco, with biosynthesis taking place in the roots, and accumulating in the leaves...
, exhibit symptoms such as irritability, jitteriness, dry mouth, and rapid heart beat. Longer abstinence may lead to
insomniaInsomnia is a symptom of any of several sleep disorders, characterized by persistent difficulty falling asleep or staying asleep despite the opportunity. Insomnia is a symptom, not a stand-alone diagnosis or a disease. By definition, insomnia is "difficulty initiating or maintaining sleep, or both"...
and even mild
depressionMajor depressive disorder is a mental disorder characterized by an all-encompassing low mood accompanied by low self-esteem, and loss of interest or pleasure in normally enjoyable activities...
. The onset of these symptoms is very fast, nicotine's half-life being only 2 hours. Withdrawal symptoms can appear even if the smoker's consumption is very limited or irregular, appearing after only 4-5 cigarettes in most adolescents. An ex-smoker's chemical dependence to nicotine will cease after approximately ten to twenty days, although the brain's number of nicotine receptors is permanently altered, and the psychological dependence may linger for months or even many years. Unlike some
recreational drugsRecreational drug use is the use of psychoactive drugs for recreational purposes rather than for work, approved medical or spiritual purposes, although the distinction is not always clear ....
, nicotine does not measurably alter a smoker's
motor skills, judgement, or
languageA language is a system for encoding and decoding information. In its most common use, the term refers to so-called "natural languages" — the forms of communication considered peculiar to humankind. In linguistics the term is extended to refer to the human cognitive facility of creating and using...
abilities while under the influence of the drug, but nicotine withdrawal symptoms such as irritability and incapacity to concentrate can have an influence on these aspects. Tobacco withdrawal has been shown to cause clinically significant distress.
Most notably, some studies have found that patients with
Alzheimer's diseaseAlzheimer's disease , also called Alzheimer disease, Senile Dementia of the Alzheimer Type or simply Alzheimer's, is the most common form of dementia. This incurable, degenerative, and terminal disease was first described by German psychiatrist and neuropathologist Alois Alzheimer in 1906 and was...
are more likely not to have smoked than the general population, which has been interpreted to suggest that smoking offers some protection against Alzheimer's. However, the research in this area is limited and the results are conflicting; some studies show that smoking increases the risk of Alzheimer's disease. A recent review of the available scientific literature concluded that the apparent decrease in Alzheimer risk may be simply due to the fact that smokers tend to die before reaching the age at which Alzheimer normally occurs. "Differential mortality is always likely to be a problem where there is a need to investigate the effects of smoking in a disorder with very low incidence rates before age 75 years, which is the case of Alzheimer's disease," it stated, noting that smokers are only half as likely as non-smokers to survive to the age of 80.
Former and current smokers have a lower incidence of
Parkinson's diseaseParkinson's disease is a degenerative disorder of the central nervous system that often impairs the sufferer's motor skills, speech, and other functions....
compared to people who have never smoked, although the authors stated that it was more likely that the movement disorders which are part of Parkinson's disease prevented people from being able to smoke than that smoking itself was protective. Another study considered a possible role of nicotine in reducing Parkinson's risk: nicotine stimulates the
dopaminergicDopaminergic means related to the neurotransmitter dopamine. For example, certain proteins such as the dopamine transporter , vesicular monoamine transporter 2 , and dopamine receptors can be classified as dopaminergic, and neurons which synthesize or contain dopamine and synapses with dopamine...
system of the brain, which is damaged in Parkinson's disease, while other compounds in tobacco smoke inhibit MAO-B, an enzyme which produces oxidative radicals by breaking down dopamine.
A very large percentage of schizophrenics smoke tobacco as a form of self medication. The high rate of tobacco use by the mentally ill is a major factor in their decreased life expectancy, which is about 25 years shorter than the general population. Following the observation that smoking improves condition of people with schizophrenia, in particular working memory deficit,
nicotine patchA nicotine patch is a transdermal patch that releases nicotine into the body through the skin. It is usually used as a method to quit smoking. The first patch appeared in 1993.-Cost:...
es had been proposed as a way to treat schizophrenia. Some studies suggest that a link exists between smoking and mental illness, citing the high incidence of smoking amongst those suffering from
schizophreniaSchizophrenia , from the Greek roots skhizein and phrēn, phren- is a psychiatric diagnosis that describes a mental disorder characterized by abnormalities in the perception or expression of reality...
and the possibility that smoking may alleviate some of the symptoms of mental illness, but these have not been conclusive.
Recent studies have linked smoking to anxiety disorders, suggesting the correlation (and possibly mechanism) may be related to the broad class of anxiety disorders, and not limited to just depression. Current ongoing research are attempting to explore the addiction-anxiety relationship.
Data from multiple studies suggest that anxiety disorders and depression play a role in cigarette smoking.
A history of regular smoking was observed more frequently among individuals who had experienced a major depressive disorder at some time in their lives than among individuals who had never experienced major depression or among individuals with no psychiatric diagnosis. People with major depression are also much less likely to
quitSmoking cessation is the process of discontinuing the practice of inhaling a smoked substance, mainly tobacco, but it may encompass cannabis or other substances.- Treatment for smoking related constipation :...
due to the increased risk of experiencing mild to severe states of depression, including a major depressive episode. Depressed smokers appear to experience more withdrawal symptoms on quitting, are less likely to be successful at quitting, and are more likely to relapse.
Evidence suggests that non-smokers are up to twice as likely as smokers to develop
Parkinson's diseaseParkinson's disease is a degenerative disorder of the central nervous system that often impairs the sufferer's motor skills, speech, and other functions....
or
Alzheimer's diseaseAlzheimer's disease , also called Alzheimer disease, Senile Dementia of the Alzheimer Type or simply Alzheimer's, is the most common form of dementia. This incurable, degenerative, and terminal disease was first described by German psychiatrist and neuropathologist Alois Alzheimer in 1906 and was...
.
A plausible explanation for these cases may be the effect of nicotine, a
cholinergicA receptor is cholinergic if it uses acetylcholine as its neurotransmitter.Cholinergic means related to the neurotransmitter acetylcholine, and is typically used in a neurological perspective. The parasympathetic nervous system is entirely cholinergic...
stimulantStimulants, also sometimes called psychostimulants, are psychoactive drugs which induce temporary improvements in either mental or physical function or both. Examples of these kinds of effects may include enhanced alertness, wakefulness, and locomotion, among others...
, decreasing the levels of
acetylcholineThe chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system and central nervous system in many organisms including humans. Acetylcholine is one of many neurotransmitters in the autonomic nervous system and the only neurotransmitter used in the motor division...
in the smoker's brain; Parkinson's disease occurs when the effect of
dopamineDopamine is a neurotransmitter occurring in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this phenethylamine functions as a neurotransmitter, activating the five types of dopamine receptors — D
1, D
2, D
3, D
4, and...
is less than that of acetylcholine. In addition, nicotine stimulates the mesolimbic dopamine pathway (as do other drugs of abuse), causing an effective increase in dopamine levels. Opponents counter by noting that consumption of pure nicotine may be as beneficial as smoking without the risks associated with smoking, although this is unlikely due to the importance of the MAO-B inhibitor compounds of tobacco in preventing neurodegenerative diseases.
In pregnancy
A number of studies have shown that tobacco use is a significant factor in
miscarriageMiscarriage or spontaneous abortion is the spontaneous end of a pregnancy at a stage where the embryo or fetus is incapable of surviving, generally defined in humans at prior to 20 weeks of gestation...
s among pregnant smokers, and that it contributes to a number of other threats to the health of the fetus. Second-hand smoke appears to present an equal danger to the fetus, as one study noted that "heavy
paternal smoking increased the risk of early pregnancy loss."
Other
Studies suggest that smoking decreases appetite, but did not conclude that overweight people should smoke or that their health would improve by smoking. Smoking also decreases weight by overexpressing the gene
AZGP1Zinc-alpha-2-glycoprotein is a protein that in humans is encoded by the AZGP1 gene.This gene expresses a soluble protein that stimulates lipolysis, induces a reduction in body fat in mice, is associated with the cachexia related to cancer, and is known to be expressed in secretory cells of lung...
which stimulates
lipolysisLipolysis is the breakdown of fat stored in fat cells. During this process, free fatty acids are released into the bloodstream and circulate throughout the body. Ketones are produced, and are found in large quantities in ketosis...
.
Preliminary reports suggest that smoking can decrease the incidence of
acneAcne is a group of skin rashes that have different causes.* Acne vulgaris - most commonly experienced around puberty, typically of the face and shoulders/chest* Cystic acne, a severe form of acne wherein small cysts form...
prophylactically. This was seen by a decreased percentage ratio of patients needing acne medication versus the percentage of entire population of smokers. (A smaller percentage of patients who smoked needed medication than found in the population as a whole).
A protective effect of current smoking against
ulcerative colitisUlcerative colitis is a form of inflammatory bowel disease . Ulcerative colitis is a form of colitis, a disease of the intestine, specifically the large intestine or colon, that includes characteristic ulcers, or open sores, in the colon. The main symptom of active disease is usually constant...
, although smoking
increases the risk of
Crohn's diseaseCrohn's disease is an inflammatory disease of the intestines that may affect any part of the gastrointestinal tract from anus to mouth, causing a wide variety of symptoms...
, the other form of
inflammatory bowel diseaseIn medicine, inflammatory bowel disease is a group of inflammatory conditions of the colon and small intestine. The major types of IBD are Crohn's disease and ulcerative colitis..-Forms:...
. There is some evidence for decreased rates of
endometriosisEndometriosis is a medical condition in women in which endometrial like cells appear and flourish in areas outside the uterine cavity. The uterine cavity is lined by endometrial cells, which are under the influence of female hormones...
in infertile smoking women, although other studies have found that smoking increases the risk in infertile women. There is little or no evidence of a protective effect in fertile women. Some preliminary data from 1996 suggested a reduced incidence of
uterine fibroidsA uterine fibroid is a non-cancerous tumor that originates from the smooth muscle layer and the accompanying connective tissue of the uterus...
, but overall the evidence is unconvincing.
A new research has found that women who smoke are at significantly increased risk of developing an abdominal aortic
aneurysmAn aneurysm or aneurism , is a localized, blood-filled dilation of a blood vessel caused by disease or weakening of the vessel wall....
, a condition in which a weak area of the abdominal aorta expands or bulges.
Several types of "Smoker’s Paradoxes", (cases where smoking appears to have specific beneficial effects), have been observed; often the actual mechanism remains undetermined. Risk of
ulcerative colitisUlcerative colitis is a form of inflammatory bowel disease . Ulcerative colitis is a form of colitis, a disease of the intestine, specifically the large intestine or colon, that includes characteristic ulcers, or open sores, in the colon. The main symptom of active disease is usually constant...
has been frequently shown to be reduced by smokers on a dose-dependent basis; the effect is eliminated if the individual stops smoking.
Smoking appears to interfere with development of
Kaposi's sarcomaKaposi's sarcoma is a tumor caused by Human herpesvirus 8 , also known as Kaposi's sarcoma-associated herpesvirus . It was originally described by Moritz Kaposi, a Hungarian dermatologist practicing at the University of Vienna in 1872. It became more widely known as one of the AIDS defining...
,
breast cancerBreast cancer is a cancer that starts in the breast, usually in the inner lining of the milk ducts or lobules. There are different types of breast cancer, with different stages , aggressiveness, and genetic makeup. With best treatment, 10-year disease-free survival varies from 98% to 10%...
among women carrying the very high risk
BRCABRCA can refer to one of several things:*BRCA1 and BRCA2, a pair of genes involved in breast cancer.*British Radio Car Association – an organisation governing all types of radio controlled car racing in the United Kingdom....
gene,
preeclampsia,
and
atopic disorderAtopy or atopic syndrome is an allergic hypersensitivity affecting parts of the body not in direct contact with the allergen.-Causes:...
s such as allergic asthma.
A plausible mechanism of action in these cases may be the
nicotineNicotine is an alkaloid found in the nightshade family of plants which constitutes approximately 0.6–3.0% of dry weight of tobacco, with biosynthesis taking place in the roots, and accumulating in the leaves...
in tobacco smoke acting as an
anti-inflammatory agentInflammation is the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli as well as initiate the healing process for the tissue. Inflammation is not a...
and interfering with the disease process.
History
The late-19th century invention of automated cigarette-making machinery in the American South made possible mass production of cigarettes at low cost, and cigarettes became elegant and fashionable among society men as the Victorian era gave way to the Edwardian. In 1912, American Dr. Isaac Adler was the first to strongly suggest that lung
cancerCancer is a class of diseases in which a group of cells display uncontrolled growth , invasion , and sometimes metastasis...
is related to smoking. In 1929, Fritz Lickint of
DresdenDresden is the capital city of the Free State of Saxony in Germany. It is situated in a valley on the River Elbe. The Dresden conurbation is part of the Saxon Triangle metropolitan area....
,
GermanyGermany , officially the Federal Republic of Germany , is a country in Central Europe. It is bordered to the north by the North Sea, Denmark, and the Baltic Sea; to the east by Poland and the Czech Republic; to the south by Austria and Switzerland; and to the west by France, Luxembourg, Belgium,...
, published a formal statistical evidence of a lung cancer–tobacco link, based on a study showing that
lung cancerLung cancer is a disease of uncontrolled cell growth in tissues of the lung. This growth may lead to metastasis, which is the invasion of adjacent tissue and infiltration beyond the lungs. The vast majority of primary lung cancers are carcinomas of the lung, derived from epithelial cells...
sufferers were likely to be smokers. Lickint also argued that tobacco use was the best way to explain the fact that lung cancer struck men four or five times more often than women (since women smoked much less).
Prior to World War I, lung cancer was considered to be a rare disease, which most physicians would never see during their career. With the postwar rise in popularity of cigarette smoking, however, came an epidemic of lung cancer.
In 1950,
Richard DollSir William Richard Shaboe Doll CH OBE FRS was a British physiologist who became the foremost epidemiologist of the 20th century, turning the subject into a rigorous science. He was a pioneer in research linking smoking to health problems...
published research in the
British Medical JournalBMJ is a partially open access medical journal. It is among the most influential and widely read peer-reviewed general academic journals in the field of medicine in the world....
showing a close link between smoking and lung cancer. Four years later, in 1954 the
British Doctors StudyThe British doctors study is the generally accepted name of a prospective cohort study which has been running from 1951 to 2001, and in 1956 provided convincing statistical proof that tobacco smoking increased the risk of lung cancer.-Context:...
, a study of some 40 thousand doctors over 20 years, confirmed the suggestion, based on which the government issued advice that smoking and lung cancer rates were related. The British Doctors Study lasted till 2001, with results published every ten years and final results published in 2004 by Doll and
Richard PetoSir Richard Peto FRS is Professor of Medical Statistics and Epidemiology at the University of Oxford.He attended Taunton's School in Southampton and subsequently studied Natural Sciences at Cambridge University....
. Much early research was also done by
Alton OchsnerAlton Ochsner was a surgeon and medical researcher who worked at Tulane University and other New Orleans hospitals before he established his own world-renowned The Ochsner Clinic, now known as Ochsner Foundation Hospital...
.
Reader's DigestReader's Digest is a monthly general-interest family magazine co-founded in 1922 by Lila Bell Wallace and DeWitt Wallace, and based in Chappaqua, New York, United States of America...
magazine for many years published frequent anti-smoking articles. In 1964 the United States
Surgeon GeneralThe Surgeon General of the United States is the operational head of the Public Health Service Commissioned Corps and thus the leading spokesman on matters of public health in the federal government...
's Report on Smoking and Health (referenced below), led millions of American smokers to quit, the banning of certain advertising, and the requirement of warning labels on tobacco products.
The Canadian province of
British ColumbiaBritish Columbia is the westernmost of Canada's provinces and is famed for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . In 1871, it became the sixth province of Canada.The capital of British Columbia is Victoria, the 15th largest metropolitan region in Canada...
has the
Tobacco Damages and Health Care Costs Recovery ActBritish Columbia's Tobacco Damages and Health Care Costs Recovery Act is approved by the Supreme Court of Canada, opening the door for the province to sue cigarette makers, in order to recover the billions spent in inflicted healthcare costs....
.