Sleep Deeply, Live Longer

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“Your nerve cells connect by sending signals to each other, and these connections are strengthened when we sleep,” Cole says. Numerous studies on athletes have proven that sleep is an important factor in gaining the “competitive edge,” because skill learning and integration happen during sleep.

Lack of sleep also may be a factor in the country’s expanding obesity epidemic. Several recent studies found that some of the hormonal changes that occur while we sleep affect our appetite. A study conducted by Stanford University’s Howard Hughes Medical Institute found that people who slept five hours a night had higher levels of ghrelin (a hormone that causes hunger) than people who slept eight hours each night. Another recent study in the Archives of Internal Medicine showed a correlation between a higher body mass index (a measure of body fat based on height and weight) and lack of sleep.

Sleep also plays an important role in building immunity. Research shows that while we’re slumbering, the body’s immune system is strengthened in ways that don’t occur when we’re awake. Consequently, scientists think that improving sleep may be an important factor in enhancing the success of vaccinations and treating certain diseases.

Mechanics of Sleep

If you’re not getting enough sleep on a regular basis, you’re most likely building up “sleep debt,” Cole says. The longer the situation persists, the greater the debt, and the only way to pay off the loan is to sleep for longer periods of time. It can take several sleep periods over days or even weeks to catch up on a significant sleep deficit.

If you’re not having trouble sleeping, you can enjoy a daytime nap, but those with sleep difficulties should avoid them, Cole says. Sleeping during the day cuts back on the amount of time you’re likely to sleep at night.

Sleep occurs in several stages that repeat cyclically throughout the night. The first stage is fairly light and occurs as we drift off to sleep. Stages one and two last about 30 minutes combined. During stages three and four, known as slow-wave sleep, our brain waves slow down the most. Finally, we enter into the deep REM (rapid eye movement) type of sleep when we do most of our intense dreaming.

Each complete cycle takes about 90 minutes, so if you’re the kind of person who likes to nap, sleeping 20 minutes or less, or napping for about 90 minutes, allows you to avoid waking up during stages three and four, which would otherwise make you feel groggy.

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