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Circadian Rhythms Are Nothing to Lose Sleep Over


Getting a good night's sleep--or a good day's sleep if you prefer--is more easily accomplished when you're in sync with your body's internal clock.


Body temperature, exposure to light and what a person eats all affect how that clock--known as circadian rhythm--runs.

While many of us use an alarm clock to awaken, research shows that when our bodies are allowed to run unencumbered by clocks, an internal gauge keeps us up and puts us to bed at certain times.

"Researchers have placed people in caves and allowed them to free-run as far as time," says sleep specialist Sarah Mosko, director of the Sleep Disorders Center at St. Joseph Hospital in Orange. "Subjects who had no access to clocks followed their own timetables, going to bed at the same time and rising at the same hour."

Some of the people studied turned out to be "night owls," who functioned best when staying up until 1 or 2 a.m., while other people were "larks" who fell asleep at 8, 9 or 10 p.m. and woke early in the morning. Others fell somewhere between.

Studies have also found that when we sleep and awaken is related to body temperature, says Mark Brayford, director of the Sleep Disorders Center at Western Medical Center in Anaheim. "When our body is cooler, we tend to sleep, and when it's warmer we're generally awake. Larks tend to cool down earlier in the evening and heat up earlier in the morning than night people, who stay heated until late at night and remain cool in the morning hours."

This explains why night owls have a hard time falling asleep until it's late and larks wake up early no matter what time they go to bed. "Our body temperature, not the clock on the wall, tells us when to sleep and when to wake up," Brayford says.

"Night people aren't lazy because they get up later, and morning people aren't strange because they go to sleep early and wake up before most people. Both types are just in different time zones," he says.

Late and early sleepers tend to sleep the same amount of time. For instance, a lark might go to bed at 10 p.m. and get up at 5:30 a.m., while a night owl won't go to bed until 1 a.m. and will arise three hours later at 8:30 a.m.

"The national average for sleep requirements is 7.5 hours, although people vary in how much they need, which can range from four to 10 hours," Mosko says.

While many night owls and larks are able to function well, some have problems meeting work and social obligations because of their sleep requirements. The good news is it is possible to reset the body's clock.

The first step to changing your clock is charting your circadian rhythm throughout a week, Brayford says. "Write down how alert you are during each hour of the day--(the number) one being asleep and 10 being very alert. To get an accurate reading, go to bed and arise at the same time every day. By the end of the week, you should see a definite pattern."

To change the pattern, begin rising at your desired wake-up time every morning, no matter what time you went to bed the night before or how poorly you slept. In most cases, after several weeks of doing this, your body will transition to the new sleep and wake times.

If you have difficulty adjusting to your new schedule or would like to speed the process, you can also add light treatment, Mosko says.

Researchers have found that light causes a rise in body temperature and wakes people. If your goal is to rise earlier, expose yourself to light as soon as you wake up. Those people who wish to stay up later and rise later should get light in the late afternoon.

For exposure to light, you can either go outdoors or buy a light box, which simulates outdoor light. These are also used for people with Seasonal Affective Disorder and come in a variety of shapes and sizes.

"Sit in front of a bright light box when you wake up in the morning or in the late afternoon for 20 minutes to two hours, depending on the light's intensity," says Mosko, who advises people to get some instruction before using a light box.

Once you set your clock at the desired times, rigidly impose your sleep and wake times. Only stay up late when necessary, especially if you are prone to being a night owl, because the tendency is to revert readily when given the chance, Mosko says.

If you try the above methods, but can't seem to budge your clock, you may need assistance. With more stubborn or severe cases, sleep disorders experts push a person forward or backward in three-hour time increments until they reach their desired time. For instance, a night owl would go to bed at 2 a.m. the first night, then 5 a.m., then 8 a.m. and so forth, sleeping the same number of hours each time. The pattern continues until the desired bedtime is reached.

Here are some ways to keep your biological clock set where you want it:

* Practice healthy sleep hygiene.

"To perform at your best, don't challenge your system by constantly staying up late and getting up early. Stick to a regular bedtime and wake time as much as possible," Mosko says.

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