Jet Lag and Sleep

Jet lag is a term for changes in the internal daily rhythms of the body (circadian rhythms) that people experience when traveling from one time zone to another. For example, traveling from the West Coast to the East Coast results in a three-hour time change. Your body will remain on the original schedule. So when the alarm clock rings at 8 a.m., your body thinks it is 5 a.m. In the short term, jet lag results in unpleasant tiredness and difficulty getting on schedule in the new time zone. Frequent travelers may suffer from more severe effects of jet lag.

Long-Term Effect of Jet Lag

While not well understood, researchers have found that routine interruption in the circadian rhythms of mice can lead to shortened life expectancy. Researchers placed both young and aged mice on an 8-week cycle of shifts in light exposure.

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In one group, the light cycle was advanced 6 hours every 7 days. Another group’s light exposure was delayed 6 hours every 7 days. A third group maintained a constant 12-hour light cycle.

The young mice did not seem affected greatly by the changes in light, but the aged mice experienced marked increases in mortality. Only 47 percent of the first group survived the study, 68 percent of the second group. This is compared to 83 percent of the control group.

Does that mean humans shorten their lives by flying? No. There isn’t enough data about human travel and circadian rhythms to know the long-term effect. But the aforementioned study, along with the known fact that jet lag increases the risk of sleep disorders like insomnia, should throw caution on routine travel that causes large changes in the daily cycle.

Reducing the Effect of Jet Lag

The body takes about 1 day per hour of change to adjust. There are no techniques to speed up that process, but you can ease the transition:

* Light therapy: Through exposure to full-spectrum lights or sunlight, a person can make the adjustment to a new time zone more gradual. This is especially effective when you can get exposure to bright lights in the last few hours of morning sleep.
* Gradual Adjustment: Before leaving on a trip, take 3 or 4 days to begin adjusting to the new schedule. Each day, sleep an hour later (or earlier) so that the change will not be as drastic. For example, if you are going to “lose” 3 hours of sleep, wake up an hour earlier each day for two days before you leave. You will adjust to the new time zone much faster that way.
* Supplements: Melatonin, valerian and other supplements may help people temporarily fall asleep faster. Consult a doctor before taking these.
* Sleep Habits: Establishing good sleep habits will really pay off when you travel. If you have trained your body to fall asleep quickly and stay asleep, you will have a much easier adjustment to the new time zone.

Sources

Chronic Jet-Lag Increase Mortality in Aged Mice. AJ Davidson, MT Sellix, J Daniel, S Yamazaki, M Menaker, and GD Block. Chronic Jet-Lag Increases Mortality in Aged Mice. Curr Biol. 2006 November 7; 16(21): R914–R916.

National Institutes of Health; National Heart, Lung and Blood Institute. Your Guide to Healthy Sleep. NIH Publication No. 06-5271.