This week's Clinical Practice review in the New England Journal of Medicine covers jet-lag. As usual for these reviews, the author presents a patient with general characteristics to focus the discussion. In this case, the patient is another physician who is about to travel from the US West Coast to London for a conference. Previous trips to Europe have been complicated by marked symptoms of jet-lag.
The author notes that jet-lag is a recognised sleep disorder caused by misalignment between a person's circadian clock and local time; it is caused by travelling across times zones too quickly for the circadian clock to keep pace. The main symptoms are insomnia and daytime sleepiness, but may also include gastro-intestinal disturbance and cognitive impairment. Although usually benign and self-limiting, it can have significant impact in those travelling for important commercial or professional reasons. Several factors influence its severity, including direction of travel (eastwards worse than westwards), number of time zones crossed, availability of local cues, and personal variation.
Three main strategies for dealing with jet-lag are recognised: therapeutic acceleration of the natural circadian clock realignment, strategic sleep scheduling, and pharmacotherapy with hypnotics or drugs to promote alertness.
The circadian clock can usually be realigned more quickly than would occur naturally using a strategy of optimised light exposure and possibly melatonin treatment. Under normal circumstances, the clock resets by about 92 minutes later per day after westward flight and 57 minutes daily after eastwards flight: speeding this up is attractive as it mimics the normal physiological processes. Circadian resetting can be hastened by careful timing of sleep and exposure to bright daylight. Melatonin can also be helpful, and has be shown to be effective in a number of controlled trials. However, optimum dose and timing remains to be confirmed. Careful use of a short-acting hypnotic may be necessary.
Strategic sleep scheduling can be effective, but requires some planning and discipline; it includes shifting sleep times a few days before departure by 1 - 2 hours towards those in the destination. Short daytime naps can reduce sleepiness after arrival, but longer sleeps are counter-productive.
A short course of a hypnotic agent has been shown to be effective in reducing sleepiness due to jet-lag. A short-acting hypnotic may also be used to promote sleep during travel; however the potential adverse effects must be considered, including potentially increased risk of travel-associated deep-vein thrombosis. In contrast, drugs that promote alertness may also be useful: caffeine has been shown to be effective, but may exacerbate insomnia, and modafinil and related drugs have been studied in trials.
Guidelines are available from the American Academy of Sleep Medicine; for the patient presented, a combination approach is suggested. This includes advancing sleep timing pre-travel, use of caffeine and exposure to bright light, and 3 to 4 days of melatonin.