Jet Lag

It's vacation season, and for many that means climbing aboard an airplane and jetting off to the beach, the mountains, or just grandma's house. If you're traveling very far, you may cross one or more time zones, gaining or losing hours. Change enough time zones in a short time and you can get a nasty case of jet lag.

Jet lag is caused by a disruption of your body's internal clock. We're set up for a regular cycle of night and day. So when you jump a few time zones and suddenly expect to be awake at 8 a.m. or asleep at 11 p.m., your body's clock is left lagging. And, although the latest research shows that the master clock in the brain quickly adjusts to the new time, the follower clocks found in the liver, the digestive track, and elsewhere in the body can take days to reset.

Jet lag often leaves people with indigestion (because their stomachs are out of sync with mealtime) or muscle twitching (because their muscles haven't fully rested). Dehydration aggravates both conditions, since the air in planes is exceptionally dry, and travelers often don't drink enough water. And the in-flight cocktail only adds to the problem, since alcohol causes dehydration and appears to further affect the body's clock.

Sleep Paralysis
A rare and little understood result of jet lag is sleep paralysis. This is a condition in which your brain wakes up before your body does—literally leaving you awake but unable to move. Because sleep paralysis is considered vastly underreported, it's difficult to determine how often it happens. Scientists say possibly as few as 5 percent to as many as 62 percent of people may experience it. But researchers agree that sleep paralysis is much more likely to happen when our regular sleep patterns are disturbed, as in jet lag. Fortunately the effect lasts only seconds, and it tends to go away after a good night's sleep.

Hardwired for 24-7
What is it about traveling across time zones that is so upsetting to our internal clock? When we cross time zones, what we're really crossing are different times that the sun rises and sets. Because Earth spins a complete turn east to west every 24 hours, the East Coast of the United States sees the sun rise about three hours earlier than the West Coast does. That means when you fly long distances east or west, you're suddenly changing when your body will see the sun—and you will need to be awake when you're usually asleep, or vice versa.

Covered in Clocks
The central part of the body's clock is a small cluster of brain cells found in the suprachiasmatic nucleus, which is in the hypothalamus. That's the part of the brain that registers pleasure and fight-or-flight reactions. But we don't rely only on the clock in the brain. Research has shown that nearly every cell of the body contains some type of timepiece.

Treating Jet Lag
The ability of bright light to reset the clock is the rationale for a prescribed treatment for jet lag—sunshine. By exposing your body to sunlight or bright artificial light at the right time, some doctors say you can "reset" your body's clock. So next time you board a plane, figure out how many hours ahead of, or behind, the sun you'll be when you arrive. That way you'll know whether to step out into the sunshine or stay in the shade when you arrive.