Managing jet lag: Some of the problems and possible new solutions

SUMMARY

Jet lag is due to the misalignment of the internal circadian clock(s) with external time cues. For short stopovers (1–2 days) adapting the circadian system is not advised, and at present immediate circadian adaptation is virtually impossible. The use of short-term measures such as judicious naps, caffeine and short acting hypnotics to maintain alertness and sleep is preferred. For intermediate length stays (3–5 days) a phase position with the circadian nadir situated within the sleep period is desirable but difficult to achieve. For longer stays (more than 4–5 days) strategies to hasten adaptation include timed exposure to and avoidance of light. The use of artificial light enriched with short wavelengths may be beneficial. The American Academy of Sleep Medicine recommends the timed use of the chronobiotic melatonin to hasten adaptation. Large individual differences in rate and direction of adaptation make timing treatment according to individual circadian phase difficult. Individual differences in tolerance to the sleep deprivation of jet lag may relate to a length polymorphism in the human clock gene PER3. The maximum efficacy for jet lag avoidance is by pre-flight adaptation, however, this requires time and commitment.

Introduction

In the last few years at least 15 reviews have addressed this subject or the broader subject of circadian rhythm sleep disorders.1, 2, 3, 4, *5, 6, 7, 8, 9, *10, 11, *12, 13, 14, *15 Rather than repeating this exercise the present review, after an introduction and summary, will consider problems of effective treatment and potential future means of managing jet lag.

Jet lag has never been completely defined, although anyone who has suffered from this problem has no difficulty in identifying their personal symptoms. It is formally described as circadian desynchrony, or a mismatch between the timing of the internal circadian (circa 24 h) clock(s) and the external environment. After an abrupt shift in time cues such as after time zone change the circadian system adapts slowly to realign with the new schedule, approximately one day for each hour of time zone change, faster westwards, with different components of the system adapting at different rates (internal desynchrony).⁵

The perceived manifestations are variable from one individual to another, with number of time zones crossed, with direction and timing of flights and probably with seasons. However, the major complaints are poor sleep, daytime fatigue and poor performance.*15, 16 Travelling eastwards, short sleep and long sleep latency are common, travelling westward short sleep and early wake up are manifest. Poor alertness and fatigue during daytime are attributed partly to sleep deprivation and partly to the concomitant presence of night time rhythm physiology – the nadir of the core body temperature, alertness, performance, metabolism and the peak of melatonin secretion. In this Olympic year of 2008 with many athletes travelling over large numbers of time zones to Beijing, the question of physical performance has been addressed in some detail.3, *5, 8 One of the earliest descriptions of the effects of jet lag on physical performance concerned American baseball players who performed significantly worse when playing away over an eastward time zone transition.¹⁷

There are possible long term consequences of frequent desynchrony as evidenced by epidemiological and animal studies.18, 19, 20, *21 These include cognitive deficits, gastrointestinal problems, increased risk of cancer, infertility and heart disease. However, not all reports are consistent. Adapting to phase shift becomes harder as we grow older for uncertain reasons.22, 23