Traveling across time zones can disrupt regular patterns of sleep and wakefulness.
Because the internal circadian alerting system is at its strongest during the daytime, night shift workers often find themselves struggling to sleep “on the wrong side of the clock.”
Good sleep habits (in particular), a regular schedule, and simple workplace measures can help shift workers get the sleep they need.
If you’ve ever traveled by plane across several times zones, chances are you’ve experienced “jet lag.” Symptoms of jet lag may include excessive daytime sleepiness, nighttime insomnia, headache, loss of appetite, gastrointestinal problems, and irritability or mild depression.
Jet lag is a result of the mismatch between the external environment and our internal biological clock. This clock is the pacemaker system that controls many different bodily functions during a 24-hour period and regulates when we sleep and when we wake up. Because plane travel is quick, someone who crosses several time zones will experience a temporary desynchronization between the new time zone schedule and his or her internal clock. For example, if you take a nine-hour flight from Chicago to Amsterdam and your plane leaves at 6:00 p.m., it will touch down at 9:00 a.m. Netherlands time. However, to your body it will feel like the middle of the night—because back in Chicago it actually is 3:00 in the morning.
Shifting to a new time zone in this way may result in sleep disturbances. This is due to circadian misalignment: your body’s internal clock is out of synch with the actual time in the new time zone. Your body feels that it is time to go to sleep when others are having breakfast, and you feel wide awake when everyone around you is fast asleep.
Fortunately, jet lag is usually temporary because our internal biological clock adapts in response to external cues in the new environment. That adaptation—in which the internal clock readjusts itself a little bit every day until it is in the normal alignment with the external environment—is called entrainment. The environmental cues that nudge the entrainment process along include exposure to light in the first few days following travel, being active, and eating meals and sleeping at appropriate times in the new time zone. It is usually advisable to avoid long daytime naps in the new time zone in order to build up enough of a drive to sleep to promote nighttime sleep.