SeminarJet-lag
Section snippets
Epidemiology
Individuals experience some or all of the symptoms of jet-lag to differing extents.1, 2, 6 Generally, symptoms are worse the older the traveller and the more time zones crossed; eastward travel is associated with worse symptoms than westward. The severity of the symptoms may also be related to phase of the menstrual cycle. Disturbances of this cycle itself are common in flight attendants.7
One of the main problems associated with jet-lag is sleep loss.8 After flights to the east the difficulty
Pathophysiology
The problems linked with jet travel are not due mainly to changes of culture, the time of the flight, the associated aggravation, or the length of the flight itself. The symptoms do not occur after long-distance flights to the south or north,2 and they can be duplicated in the laboratory, where the only change is to local time.4
The explanation for jet-lag is that it is due to transient dissociation between the environmental (local time in the new time zone) and internal (body time due to the
Prevention and treatment
To be valuable, a method of prevention or treatment should be effective, cause no side-effects, and be convenient to the user; it should also be readily available. Several methods have been advocated:4, 29, 30 some aim to reduce the amount of jet-lag that might be experienced, others aim to alleviate the symptoms of jet-lag when they occur, and others are intended to promote adjustment of the body clock to the new time zone. Of these three approaches, the last is appropriate only if the
Adjustment of the body clock
If some means for adjustment of the body clock is to be used, its timing depends on that of the body clock, not local time. Thus, procedures normally effective in the evening or in the early morning might need to be applied at inconvenient times, and times just before or after the temperature minimum might be less inconvenient than first appears, since they no longer fall in the middle of sleep (figure 2)
Studies involving real38 or simulated38, 39 time-zone transitions and computer-based
Non-pharmacological phase shifting
There are tables (table 2)14 and computer programs50 that advise on when to attempt exposure to, or avoidance of, bright light. They are based on the observations that bright light in the morning (0500–1100 h) on body time advances the clock, and bright light in the evening (2200–0400 h) on body time delays it. As a supplement to this treatment, there are also times when light should be avoided (those times that produce a shift of the body clock in the direction opposite to that desired).
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