Jet lag

Wilderness medicine and outdoor persons are commonly world travelers. Jet lag is a sleep disorder that results from crossing time zones too rapidly for the human biologic circadian “clock,” which is synchronized to the sun’s cycle of light and darkness, to keep pace. It has been estimated that the circadian clock resets an average of approximately 90 minutes later each day after a westward flight and approximately 60 minutes earlier each day after an eastward flight. Many people notice that it’s more difficult from a jet lag perspective when traveling from west to east. Diet and exercise don’t have any known effect on jet lag, but when optimized, might make a person feel better and therefore be conducive to restful sleep.

Here are strategies recommended by sleep experts for managing jet lag:

• Reset the circadian clock by using appropriately timed exposure to light. One shifts the clock to a later time by exposure to light in the evening and shifts it to an earlier time by exposure to light in the morning. To keep it simple, when traveling eastward across up to eight time zones, one should seek exposure to bright light in the morning. When traveling westward across up to eight time zones, one should seek exposure to bright light in the evening. An additional recommendation for travel across more than 8 time zones is to stay indoors (e.g., avoid sunlight) for the first few hours of daylight after long eastward flights or for a few hours before dusk after long westward flights.

• Take the hormone melatonin, which is normally secreted by the body for roughly 10 to 12 hours at night. It can be considered to be a darkness signal, with effects opposite those of exposure to light. Therefore, if melatonin is taken in the evening before it would normally be secreted, it resets the body clock to an earlier time, and when it is taken in the morning, it resets the clock to a later time. To promote shifting of the body clock to a later time (when you’re traveling westward), take 0.5 mg (a short-acting dose) during the second half of the night until you have become adapted to local time. To promote shifting of the body clock to an earlier time (when you’re traveling eastward), take 0.5 to 3 mg at local bedtime nightly until you have become adapted to local time.

Most people simply try to power through jet lag, but there is a science to it. To make a coordinated effort to minimize jet lag, here are additional recommendations, depending on whether a person is traveling westward or eastward: