Chapter 2The Pre-Travel ConsultationSelf-Treatable Conditions
Jet lag is a temporary sleep disorder among air travelers who rapidly travel across ≥3 time zones. Jet lag occurs as a result of the slow adjustment of the body clock to the destination time. Consequently, the daily rhythms and the internal drive for sleep and wakefulness are out of synchronization with the new environment.
The intrinsic body clock resides in the suprachiasmatic nuclei at the base of the hypothalamus, which contains melatonin receptors. 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, mainly the light–dark cycle, and the rhythmic secretion of melatonin. Exercise is also believed to exert an effect on the body clock, although with a somewhat weaker effect than other cues.
RISK FOR TRAVELERS
Eastward travel is associated with difficulty falling asleep at the destination bedtime and difficulty arising in the morning. Westward travel is associated with early evening sleepiness and predawn awakening at the travel destination. Travelers flying within the same time zone typically experience the fewest problems, such as nonspecific travel fatigue. Crossing more time zones or traveling eastward generally increases the time required for adaptation. After eastward flights, jet lag lasts for the number of days roughly equal to two-thirds the number of time zones crossed; after westward flights, the number of days is roughly half the number of time zones.
Individual responses to crossing time zones and ability to adapt to a new time zone vary. Increased age may contribute to a longer recovery period. The intensity and duration of jet lag are related to the number of time zones crossed, the direction of travel, the ability to sleep while traveling, the availability and intensity of local circadian time cues at the destination, and individual differences in phase tolerance.
Jet-lagged travelers may experience the following symptoms:
- 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 physical and mental tasks during the new daytime
- Negative subjective changes such as fatigue, headache, irritability, stress, inability to concentrate, and depression
- Gastrointestinal disturbances and decreased interest in and enjoyment of meals
Travelers can minimize jet lag by doing the following before travel:
- Exercise, eat a healthful diet, and get plenty of rest.
- Begin to reset the body clock by shifting the timing of sleep to 1–2 hours later for a few days before traveling westward and shifting the timing of sleep to 1–2 hours earlier for a few days before traveling eastward. It can also be helpful to shift mealtimes to hours that coincide with these changes.
- Seek exposure to bright light in the evening if traveling westward, in the morning if traveling eastward (although it requires high motivation and strict compliance with the prescribed light–dark schedules).
- Break up a long journey with a stopover, if possible.
Travelers should do the following during travel:
- Avoid large meals, alcohol, and caffeine.
- Drink plenty of water to remain hydrated.
- Move around on the plane to promote mental and physical acuity, as well as protect against deep vein thrombosis.
- Wear comfortable shoes and clothing.
- Sleep, if possible, during long flights.
Travelers should do the following on arrival at the destination:
- Avoid situations requiring critical decision making, such as important meetings, for the first day after arrival.
- Adapt to the local schedule as soon as possible.
- Depending on the number of time zones crossed, people with diabetes may need to adjust their insulin schedule during travel and on arrival at their destination. Providers should work with their patients to arrange schedule changes before travel.
- Optimize exposure to sunlight after arrival from either direction. Exposure to bright light in the morning moves the stage of circadian rhythm forward, while exposure to light in the evening delays the stage and encourages later sleep.
- Eat meals appropriate to the local time, drink plenty of water, and avoid excess caffeine or alcohol. Eat a balanced diet, including carbohydrates.
- Take short naps (20–30 minutes) to increase energy but not undermine nighttime sleep.
The use of the nutritional supplement melatonin is controversial for preventing jet lag. Some clinicians advocate the use of 0.5–5.0 mg of melatonin during the first few days of travel, and data suggest its efficacy. However, its production is not regulated by the Food and Drug Administration, and contaminants have been found in commercially available products. Current information also does not support the use of special diets to ameliorate jet lag.
The 2008 American Academy of Sleep Medicine recommendations include the following:
- Remain on home time if the travel period is 2 days or less.
- Promote sleep with hypnotic medication, although the effects of hypnotics on daytime symptoms of jet lag have not been well studied.
- Nonaddictive sedative hypnotics (non-benzodiazepines), such as zolpidem, have 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 of interaction with hypnotics should be emphasized with patients.
- If necessary, promote daytime alertness with a stimulant such as caffeine in limited quantities. Avoid caffeine after midday.
- Take short naps (20–30 minutes), shower, and spend time in the afternoon sun.
(See also the Self-Treatable Conditions section earlier in this chapter.)
- Barion A, Zee PC. A clinical approach to circadian rhythm sleep disorders. Sleep Med. 2007 Sep;8(6):566–77.
- Daurat A, Benoit O, Buguet A. Effects of zopiclone on the rest/activity rhythm after a westward flight across five time zones. Psychopharmacology (Berl). 2000 Apr;149(3):241–5.
- Dubocovich ML, Markowska M. Functional MT1 and MT2 melatonin receptors in mammals. Endocrine. 2005 Jul;27(2):101–10.
- Erren TC, Falaturi P, Morfeld P, Knauth P, Reiter RJ, Piekarski C. Shift work and cancer: the evidence and the challenge. Deutsches Arzteblatt international. 2010 Sep;107(38):657–62.
- Herxheimer A. Jet lag. Clin Evid. 2005 Jun(13):2178–83.
- Jamieson AO, Zammit GK, Rosenberg RS, Davis JR, Walsh JK. Zolpidem reduces the sleep disturbance of jet lag. Sleep Med. 2001 Sep;2(5):423–30.
- Reid KJ, Chang AM, Zee PC. Circadian rhythm sleep disorders. Med Clin North Am. 2004 May;88(3):631–51, viii.
- Reilly T, Waterhouse J, Edwards B. Jet lag and air travel: implications for performance. Clin Sports Med. 2005 Apr;24(2):367–80, xii.
- Sack RL. Clinical practice. Jet lag. N Engl J Med. 2010 Feb 4;362(5):440–7.
- Sack RL, Auckley D, Auger RR, Carskadon MA, Wright KP Jr, Vitiello MV, et al. Circadian rhythm sleep disorders: part I, basic principles, shift work and jet lag disorders. An American Academy of Sleep Medicine review. Sleep. 2007 Nov 1;30(11):1460–83.
- Waterhouse J, Edwards B, Nevill A, Atkinson G, Reilly T, Davies P, et al. Do subjective symptoms predict our perception of jet-lag? Ergonomics. 2000 Oct;43(10):1514–27.
- Waterhouse J, Reilly T, Atkinson G, Edwards B. Jet lag: trends and coping strategies. Lancet. 2007 Mar 31;369(9567):1117–29.