Jet lag
Encyclopedia
Jet lag, medically referred to as desynchronosis, is a physiological condition which results from alterations to the body's circadian rhythm
Circadian rhythm
A circadian rhythm, popularly referred to as body clock, is an endogenously driven , roughly 24-hour cycle in biochemical, physiological, or behavioural processes. Circadian rhythms have been widely observed in plants, animals, fungi and cyanobacteria...

s; it is classified as one of the circadian rhythm sleep disorder
Circadian rhythm sleep disorder
Circadian rhythm sleep disorders are a family of sleep disorders affecting, among other things, the timing of sleep. People with circadian rhythm sleep disorders are unable to sleep and wake at the times required for normal work, school, and social needs. They are generally able to get enough sleep...

s. Jet lag results from rapid long-distance transmeridian (east–west or west–east) travel, as on a jet plane.

The condition of jet lag may last several days, and a recovery rate of one day per time zone
Time zone
A time zone is a region on Earth that has a uniform standard time for legal, commercial, and social purposes. In order for the same clock time to always correspond to the same portion of the day as the Earth rotates , different places on the Earth need to have different clock times...

 crossed is a fair guideline
Guideline (medical)
A medical guideline is a document with the aim of guiding decisions and criteria regarding diagnosis, management, and treatment in specific areas of healthcare...

.

Cause

Jet lag is a chronobiological-related problem, similar to issues often induced by shift work. When traveling across a number of time zone
Time zone
A time zone is a region on Earth that has a uniform standard time for legal, commercial, and social purposes. In order for the same clock time to always correspond to the same portion of the day as the Earth rotates , different places on the Earth need to have different clock times...

s, the body clock will be out of synchronization with the destination time, as it experiences daylight and darkness contrary to the rhythms to which it has grown accustomed: the body's natural pattern is upset, as the rhythms that dictate times for eating, sleeping, hormone regulation and body temperature variations no longer correspond to the environment nor to each other in some cases. To the degree that the body cannot immediately realign these rhythms, it is jet lagged.

The speed at which the body adjusts to the new schedule depends on the individual; some people may require several days to adjust to a new time zone, while others experience little disruption. Crossing one or two time zones does not typically cause jet lag.

The condition is not linked to the length of flight, but to the trans-meridian (west–east) distance traveled. A ten-hour flight from Europe to southern Africa does not cause jet lag, as travel is primarily north–south. A five-hour flight from the east to the west coast of the United States may well result in jet lag.

Crossing the International Date Line
International Date Line
The International Date Line is a generally north-south imaginary line on the surface of the Earth, passing through the middle of the Pacific Ocean, that designates the place where each calendar day begins...

 does not contribute to jet lag, as the guide for calculating jet lag is the number of time zones crossed, and the maximum possible disruption is plus or minus 12 hours. If the time difference between two locations is greater than 12 hours, subtract that number from 24. Note, for example, that the time zone GMT+14 will be at the same time of day as GMT−10, though the former is one day ahead of the latter.

Symptoms

The symptoms of jet lag can be quite varied, depending on the amount of time zone alteration, time of day and individual differences. They may include the following:
  • Headaches
  • Fatigue, irregular sleep patterns, insomnia
    Insomnia
    Insomnia is most often defined by an individual's report of sleeping difficulties. While the term is sometimes used in sleep literature to describe a disorder demonstrated by polysomnographic evidence of disturbed sleep, insomnia is often defined as a positive response to either of two questions:...

  • Disorientation, grogginess, irritability
    Irritability
    Irritability is an excessive response to stimuli. The term is used for both the physiological reaction to stimuli and for the pathological, abnormal or excessive sensitivity to stimuli; It is usually used to refer to anger or frustration....

  • Mild depression
    Depression (mood)
    Depression is a state of low mood and aversion to activity that can affect a person's thoughts, behaviour, feelings and physical well-being. Depressed people may feel sad, anxious, empty, hopeless, helpless, worthless, guilty, irritable, or restless...

  • Constipation
    Constipation
    Constipation refers to bowel movements that are infrequent or hard to pass. Constipation is a common cause of painful defecation...

     or diarrhea
    Diarrhea
    Diarrhea , also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide. The loss of fluids through diarrhea can cause dehydration and...



Jet lag has been measured with simple analogue scales but a study has shown that these are relatively blunt for assessing all the problems associated with jet lag. The Liverpool Jet lag Questionnaire was developed to measure all the different symptoms of jet lag at several times of day, and this dedicated measurement tool has been used to assess jet lag in athletes.Waterhous et al., 2002

Management

It is possible to minimize the effects of jet lag by following some basic steps before, during, and after the flight. Full details of these steps can be found in two reviews published in the Lancet. There is also a position statement from the European College of Sports Science for management of jet lag in athletes.

Before the flight

It is recommended to visit the doctor to plan a coping strategy for medical conditions that require monitoring, including when to take medications or any other necessary detail.

One tactic is to attempt to partially adapt to the destination time zone in advance. This includes starting the daily routine one hour before or after one normally does during the week before departure. The use of a light box might help speed up the body's body clock adjustment significantly.

During the flight

To avoid dehydration
Dehydration
In physiology and medicine, dehydration is defined as the excessive loss of body fluid. It is literally the removal of water from an object; however, in physiological terms, it entails a deficiency of fluid within an organism...

, passengers are discouraged from taking alcoholic beverages and caffeine
Caffeine
Caffeine is a bitter, white crystalline xanthine alkaloid that acts as a stimulant drug. Caffeine is found in varying quantities in the seeds, leaves, and fruit of some plants, where it acts as a natural pesticide that paralyzes and kills certain insects feeding on the plants...

, as caffeine disrupts sleeping schedules. It is recommended to drink plenty of water to help counteract the effects of the dry atmosphere inside the plane.

One option to counteract jet lag is to break the trip into smaller segments if it is too long and stay overnight in some city. Additionally, it may be advisable to adjust sleeping hours on the plane to match the destination time.

Upon arrival

A helpful way to minimize jet lag is to adapt to the local time and eat accordingly. Also, exposure to sunlight
Sunlight
Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon.When the direct solar radiation is not blocked...

 during the day is helpful.

Direction of travel

There seems to be some evidence that for most people, traveling west to east is more disruptive. This may be because most people have a circadian period
Circadian rhythm
A circadian rhythm, popularly referred to as body clock, is an endogenously driven , roughly 24-hour cycle in biochemical, physiological, or behavioural processes. Circadian rhythms have been widely observed in plants, animals, fungi and cyanobacteria...

 which is a bit longer than 24 hours, making it easier to stay up later than to get up earlier.

It may also be that flights to the east are more likely to require people to stay awake more than one full night in order to adjust to the local time zone. For example, comparing a typical schedule for a traveller flying to the west vs a traveller flying to the east:
  • Westbound from London to Los Angeles. Time zone difference: 8 hours.
    Westbound Biological clock
    London local time
    Los Angeles local time
    Departure JAN 29 – 10:05 JAN 29 – 02:05
    Arrival JAN 29 – 21:10 JAN 29 – 13:10
    Bedtime JAN 30 – 06:00 JAN 29 – 22:00
  • Eastbound from Los Angeles to London.
    Eastbound Biological clock
    Los Angeles local time
    London local time
    Departure JAN 29 – 15:50 JAN 29 – 23:50
    Arrival JAN 30 – 02:00 JAN 30 – 10:00
    Bedtime JAN 30 – 14:00 JAN 30 – 22:00


The first scenario is equivalent to staying up all night and going to bed at 6 a.m. the next day—8 hours later than usual. But the second scenario (eastward) is equivalent to staying up all night and going to bed at 2 p.m. the next day—14 hours after the time one would otherwise have gone to bed. Some sleep onboard may help the situation somewhat.

The red-eye flight
Red-eye flight
A red-eye flight is any flight departing late at night and arriving early the next morning. The term red-eye derives from the fatigue symptom of having red eyes, which can be caused or aggravated by late-night travel....

 is another eastward scenario, for example flights departing the west coast of the US at midnight (PST/PDT) and arriving on the east coast early in the morning (EST/EDT). Relative to the shorter flight time and the time zones advanced, the body gets less than optimal rest to begin a day of activity.

Remedies

Since the experience of jet lag varies among individuals, it is difficult to assess the efficacy of any single remedy. Gradual adjustment over the course of several days of the onset of sleep while maintaining its regular length of 7–8 hours can reduce fatigue and prevent depression. When the goal is to catch-up with local time (vs. fallback to), this can be aided by avoiding afternoon naps and eating an early and carbohydrates-rich, low-protein dinner.

Most chemical and herbal remedies, including the hormone melatonin
Melatonin
Melatonin , also known chemically as N-acetyl-5-methoxytryptamine, is a naturally occurring compound found in animals, plants, and microbes...

, have not been tested nor approved by official agencies such as the United States Food and Drug Administration. Few studies have tested the use of melatonin for jet lag and have given mixed results, likely because the timing of administration needs to be precise and individualized.

Melatonin

Melatonin is present in the bloodstream naturally in differing amounts according to the time of day. It is produced by the pineal gland
Pineal gland
The pineal gland is a small endocrine gland in the vertebrate brain. It produces the serotonin derivative melatonin, a hormone that affects the modulation of wake/sleep patterns and seasonal functions...

 in darkness; secretion stops when there is light to the eyes. It plays a key role in the circadian rhythm which regulates various significant body functions.

A 2005 study showed that melatonin was effective in helping people fall asleep at doses of 0.3 milligrams (mg). Then, to treat the jet lag, the recommended dose of melatonin is 0.3–0.5 mg, to be taken the first day of traveling. Administration of higher doses can cause sleepiness, lethargy, confusion
ConFusion
ConFusion is an annual science fiction convention organized by the Stilyagi Air Corps and its parent organization, the Ann Arbor Science Fiction Association. Commonly, it is held the third weekend of January. It is the oldest science fiction convention in Michigan, a regional, general SF con...

, and decreased mental sharpness.

A position statement on the use of melatonin for alleviating jet lag in athletes was published in the British Journal of Sports Medicine. Melatonin is not recommended for people with the symptoms of severe mental illness
Mental illness
A mental disorder or mental illness is a psychological or behavioral pattern generally associated with subjective distress or disability that occurs in an individual, and which is not a part of normal development or culture. Such a disorder may consist of a combination of affective, behavioural,...

, severe allergies, autoimmune disease
Autoimmune disease
Autoimmune diseases arise from an overactive immune response of the body against substances and tissues normally present in the body. In other words, the body actually attacks its own cells. The immune system mistakes some part of the body as a pathogen and attacks it. This may be restricted to...

s, immune system cancers, or pregnant women.

Light therapy

The body requires approximately one day per time zone to adjust its circadian rhythm. A manufacturer of light-therapy
Light therapy
Light therapy or phototherapy consists of exposure to daylight or to specific wavelengths of light using lasers, light-emitting diodes, fluorescent lamps, dichroic lamps or very bright, full-spectrum light, usually controlled with various devices...

 lamps claims that using light therapy can speed this process up to one hour per time zone when used at the correct time, combined with avoiding light during specific periods.

Starvation

A 2008 animal study suggested that lack of food helps to override the light-controlled circadian body clock. One of its authors suggested in a statement that "a period of fasting with no food at all for about 16 hours is enough to engage this new clock. [...] The neat thing about this second clock is that it can override the main clock [...] and you should just flip into that new time zone in one day". One approach to implement this would be to eat nothing on the plane and starve until it is breakfast time at the destination.

Viagra

A recent study in hamster
Hamster
Hamsters are rodents belonging to the subfamily Cricetinae. The subfamily contains about 25 species, classified in six or seven genera....

s showed that sildenafil citrate (known commercially as Viagra) aided in a 50% faster recovery from shifts comparable to eastward travel experienced by humans and was effective starting at low doses. However, this use has not been tested in humans and is considered an off-label use
Off-label use
Off-label use is the practice of prescribing pharmaceuticals for an unapproved indication or in an unapproved age group, unapproved dose or unapproved form of administration...

 by the drug's manufacturers.

The presence of low-level light at night accelerates recovery rates in both east- and west-travelling hamsters of all ages by 50%; this is thought to be related to simulation of moonlight.

See also

  • Chronobiology
    Chronobiology
    Chronobiology is a field of biology that examines periodic phenomena in living organisms and their adaptation to solar- and lunar-related rhythms. These cycles are known as biological rhythms. Chronobiology comes from the ancient Greek χρόνος , and biology, which pertains to the study, or science,...

  • Light therapy
    Light therapy
    Light therapy or phototherapy consists of exposure to daylight or to specific wavelengths of light using lasers, light-emitting diodes, fluorescent lamps, dichroic lamps or very bright, full-spectrum light, usually controlled with various devices...

  • Red-eye flight
    Red-eye flight
    A red-eye flight is any flight departing late at night and arriving early the next morning. The term red-eye derives from the fatigue symptom of having red eyes, which can be caused or aggravated by late-night travel....

    , an overnight east-bound flight with insufficient time to get fully rested.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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