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Glenn D. Braunstein, M.D.

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Time Travel 101: Managing Jet Lag Across Time Zones

Posted: 05/03/10 04:33 PM ET

By the time you've navigated airport traffic, battled long check-in lines and consumed some bad in-flight food, you settle into your seat and realize you forgot to prepare for jet lag. But as you start crossing time zones, that headachy, sleep-deprived feeling doesn't have to ruin your vacation or business trip. Jet lag is a common sleep disorder, known medically as "desynchronosis" because it occurs when the body's circadian (24-hour) clock, becomes out of sync with the new time zone. As your internal clock struggles to realign its own normal rhythms with those of the new destination, you'll be jet lagged.

The expected challenges of travel, such as changes in temperature and eating times, can contribute to travel fatigue. Combined with the confusion your body clock is already dealing with, sleep deprivation tends to pile on the feeling of sluggishness.

The body knows what time it is by what it sees. Light signals the optic nerve to send a message to the hypothalamus, which, at the appropriate time of day, will trigger sleep, hunger and thirst, and regulate bodily functions like temperature and hormones. For example, when the sun sets and the optic nerve perceives darkness, it alerts the hypothalamus to begin releasing melatonin, a naturally occurring hormone that regulates sleepiness. As the night wanes and morning light becomes more pronounced, melatonin production slows down and stops.

Traveling across time zones confuses the hypothalamus. When its normal rhythms of perceiving light and dark are changed, sleep patterns are interrupted. Studies show that the loss of just one and a half hours of sleep can result in a 32 percent reduction in daytime alertness. Other short-term consequences of missed sleep are impaired memory and speech functions, as well as an impaired ability to think and process information.

Given that light is the essential factor in jet lag, the direction you're traveling is more important than the length of the flight. Even a 10-hour flight from Europe to southern Africa won't cause appreciable jet lag because that journey is primarily north-south; but a five-hour west-to-east flight from Los Angeles to New York probably will leave you jet lagged.

A flight of less than four hours might cause you to have stiffness and irritability, but after more than four hours, in addition to sleep deprivation, you're prone to experiencing symptoms as varied as digestive problems, dehydration, headaches, insomnia, disorientation, mild depression, anxiety, nausea or constipation. In extreme cases, body pain and memory loss might also manifest.

The general rule is that it takes about a day to adjust for every time zone crossed. Jet lag is more pronounced when traveling east because the body has to adjust to a shorter day and the body's circadian clock resets slower going in an eastward direction than westward. Traveling west creates more light and a longer day, which is an easier adjustment for the body.

There are several strategies to help avoid or minimize jet lag. Try shifting your sleep schedule by 1-2 hours before leaving home. Additionally, the use of short-acting sleeping pills like Sonata during an overnight flight may help reduce the initial sleep deprivation. Once you arrive at your destination, do what you can to realign your circadian clock. For travelers crossing up to 8 time zones, exposure to light in the morning when traveling eastward moves the clock backwards, while exposure in the evening when traveling westward shifts it to a later time.

Melatonin, which is sold over-the-counter, has been shown in several clinical trials to be helpful, although it is not FDA approved for use to treat jet lag. When traveling eastward, taking 0.5-3 mg at bedtime after arrival may speed up the shift. After traveling westward, taking 0.5 mg during the second half of the night may decrease jet lag. For a few nights after arrival, the use of a sleeping pill such as Ambien or Lunesta may help to adjust sleep to the local time. A strong cup of caffeinated java in the morning may improve alertness. Finally, a 20-minute nap in the afternoon may help recharge the batteries without inhibiting sleep at night.

Long trips can result in dehydration, so drinking a cup of water every hour you're in flight goes a long way toward minimizing the effects. Keeping your circulation up to speed is important, too, in order to avoid blood clots. So get out of your seat and walk around the plane periodically and stretch your legs. If you're prone to indigestion or nausea, take along some ginger tea.

Rather than trying to fight the effects of jet lag once they've occurred, understand what your body is trying to do to regulate itself and help it along. You just might be able to take some of the lag out of jet lag.