Jet lag, a condition that can cause fatigue or sleep difficulties for a person who is traveling across multiple time zones, might be able to be reduced if the person takes precautions to alter his or her circadian rhythms in the days before traveling. The term "circadian rhythms" refers to the body’s natural 24-hour cycle of alertness, which is largely affected by light exposure. Scientists have found that being exposed to bright light for about three hours after waking up in the days before traveling might help people who are traveling eastward to adjust to their destination’s later time zone. Westward travelers might benefit from light exposure during the three hours before they go to sleep to help them wake up later.
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