Emad Yanni

Description

Jet lag is a temporary disorder among air travelers who rapidly travel across three or more time zones. Jet lag results from the slow adjustment of the body clock to the destination time, so that daily rhythms and the internal drive for sleep and wakefulness are out of synchrony with the new environment.

The intrinsic body clock resides in the suprachiasmatic nuclei at the base of the hypothalamus, which contains melatonin receptors. The body clock receives information about light from the eyes and is also thought to receive input via the intergeniculate leaflet that carries information about physical activities and general excitement. Melatonin is manufactured in the pineal gland from tryptophan, and its synthesis and release are stimulated by darkness and suppressed by light; consequently, the secretion of melatonin is responsible for setting our sleep–wake cycle. The body clock is adjusted to the solar day by rhythmic cues in the environment known as zeitgebers (time-givers). The main zeitgebers are the light–dark cycle and this rhythmic secretion of melatonin. Exercise might also exert a weaker effect on the body clock than other zeitgebers. Although incompletely understood, the body clock is partly responsible for the daily rhythms in core temperature and plasma hormone concentrations as well.

Occurrence

• Eastward travel is associated with difficulty in falling asleep at the destination bedtime and difficulty arising in the morning.
• Westward travel is associated with early evening sleepiness and predawn awakening.
• Travelers flying within the same time zone typically experience the fewest problems.
• Crossing more time zones or traveling eastward generally increases the time required for adaptation.
• Jet lag lasts for several days, roughly equal to two-thirds the number of time zones crossed for eastward flights, and about half the number of time zones crossed after westward flights.

Risk for Travelers

• Individual responses to crossing time zones and the ability to adapt to new time zones vary. The intensity and duration of jet lag are related to the following:
  • Number of time zones crossed
  • Direction of travel
  • Ability to sleep while traveling
  • Availability and intensity of local circadian time cues at the destination
  • Individual differences in phase tolerance
• Although more data are needed, risk factors cited by the American Academy of Sleep Medicine include the following:
  • Older individuals tend to experience fewer jet lag symptoms than those who are younger.
  • Exposure to local (natural) light-dark cycle usually accelerates adaptation after jet travel over 2 to 10 time zones

Clinical Presentation

Signs of jet lag include the following:

• Poor sleep, including delayed sleep onset (after eastward flight), early awakening (after westward flight), and fractionated sleep (after flights in either direction).
• Poor performance in both physical and mental tasks during the new daytime.
• Negative subjective changes, such as increased fatigue, frequency of headaches and irritability, and decreased ability to concentrate.
• Gastrointestinal disturbances (indigestion, frequency of defecation, and the altered consistency of stools) and decreased interest in and enjoyment of meals.

Preventive Measures for Travelers

Prior to Travel

• Stay healthy by continuing to exercise, eating a nutritious diet, and getting plenty of rest.
• Consider timed bright light exposure prior to and during travel (although it requires high motivation and strict compliance with the prescribed light-dark schedules).
• Break up the journey with a stop-over.

Note: The use of the nutritional supplement melatonin is controversial for the prevention of jet lag. Some clinicians advocate the use of 0.5 mg to 5 mg of melatonin during the first few days of travel, and there are data to suggest its efficacy. However, the quality control of its production is not regulated by the U.S. Food and Drug Administration, and contaminants have been found in commercially available products.

Current information does not support the use of special diets to ameliorate jet lag.

During Travel

Travelers should be advised to—

• Avoid large meals, alcohol, and caffeine.
• Drink plenty of water.
• Move around on the plane to promote mental and physical acuity.
• Wear comfortable shoes and clothing.
• Sleep, if possible, during long flights.

On Arrival at the Destination

Travelers should be advised to—

• Avoid situations requiring critical decision-making, such as important meetings, on the first day after arrival.
• Adapt to the local schedule as soon as possible. However, if the travel period is 2 days or less, travelers should remain on home time.
• Optimize exposure to sunlight following arrival in either direction.
• Eat meals appropriate to the local time.

Treatment

• The 2008 American Academy of Sleep Medicine (AASD) recommendations include promoting sleep with hypnotic medication, although the effects of hypnotics on daytime symptoms of jet lag have not been well studied.
• The prescription of nonaddictive sedative hypnotics (nonbenzodiazepines), such as zolpidem, has been shown in some studies to promote longer periods of high-quality sleep. If a benzodiazepine is preferred, a short-acting one, such as temazepam, is recommended to minimize oversedation the following day.
• Because alcohol intake is often high during international travel, the risk for interaction with hypnotics should be emphasized with patients.

References

1. Waterhouse J, Reilly T, Atkinson G, et al. Jet lag: trends and coping strategies. Lancet. 2007;369(9567):1117–29.
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3. Reid KJ, Chang AM, Zee PC. Circadian rhythm sleep disorders. Med Clin North Am. 2004;88(3):631–51.
4. Waterhouse J, Edward B, Nevill A. et al. Do subjective symptoms predict our perception of jet lag? Ergonomics. 2000;43(10):1514–27.
5. Sack RL, Auckley D, Auger RR, et al. Circadian rhythm sleep disorders: part 1, basic principles, shift work and jet lag disorders: An American Academy of Sleep Medicine Review. Sleep. 2007;30(11):1460–83.
6. Jamieson AO, Zammit GK, Rosenberg RS, et al. Zolpidem reduces the sleep disturbance of jet lag. Sleep Med. 2001;2(5):423–30.
7. Daurat A, Benoit O, Buguet A. Effects of zopiclone on the rest/activity rhythm after a westward flight across five time zones. Psychopharmacology. 2000;149(3):241–5.
8. Reilly T, Waterhouse J, Edwards B. Jet lag and air travel: implications for performance. Clin Sports Med. 2005;24(2):367–80.
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