By Dr. Gregg D. Jacobs

Exercise as a Sleep Aid
Although most of us are aware that exercise can improve physical health, it can also improve sleep. It does this by producing a significant rise in body temperature that is followed by a compensatory drop a few hours later. The drop in body temperature, which persists for two to four hours after exercise, makes it easier to fall asleep and stay asleep.

The beneficial effect of exercise on sleep is greatest when exercise occurs within three to six hours of bedtime. Exercising closer than three hours to bedtime, however, can make it more difficult to fall asleep for body temperature may then be too elevated. This means that you will sleep better if you exercise in the late afternoon or early evening.

In one example of the beneficial effect of exercise on sleep, Stanford University School of Medicine researchers studied the effects of exercise on the sleep patterns of adults aged 55 to 75 that were sedentary and troubled by insomnia. These adults were asked to exercise for 20-30 minutes every other day in the afternoon by walking, engaging in low impact aerobics and riding a stationary bicycle.

The result? The time required to fall asleep was reduced by one-half and sleep time increased by almost one hour.

Exercise also improves sleep because it improves psychological functioning by serving as an outlet for the body's excessive tension, providing a healthy way to release anger and anxiety. Exercise has a tranquilizing effect that reduces anxiety more effectively than many anti-anxiety medications. Studies have found that the tranquilizing effect follows within five to ten minutes of completing exercise and lasts for at least four hours.

Therefore, physically active people are less likely to develop mental health problems such as anxiety and depression. Some studies have shown that exercise is the single best method for changing a bad mood. This mood enhancing effect is the result of lessening tension and increasing energy.

Exercise also improves sleep because it reduces depression, which can disturb sleep. In one study, mild to moderately depressed people reported feeling better within one week of beginning an exercise program; they also improved more over time than mild to moderately depressed people who received either short-term or long-term psychotherapy. In a study that compared the antidepressant Zoloft to exercise for the treatment of mild to moderate depression, exercise worked as well as Zoloft and did a better job of keeping the depression away once it had lifted.

Bright Light
Sleep and body temperature are directly influenced by the effect of the daily cycles of light and darkness on melatonin, a naturally occurring hormone found in the brain.

When sunlight enters the eyes, melatonin levels decrease, which signals body temperature to rise and promote wakefulness. Darkness causes melatonin levels to rise and body temperature to fall, which promotes sleep.

Consider how for almost our entire evolution as hunter-gatherers, we were exposed to the natural cycles of sunlight during the day and darkness at night. However, with the advent of modern technology, we have significantly altered our exposure to natural light and darkness. Studies have shown that, no matter where people live, they obtain only one hour of sunlight on average during the day. The nighttime lighting of urban environments means that many people also don't receive exposure to true darkness anymore.

The main reason why we obtain so little sunlight is that most of us work indoors. A brightly lit room has about 500 luxes of light (a lux is the equivalent of the light from one candle) compared to 10,000 luxes at sunrise and 100,000 at noon on a summer day. To the brain, spending the day indoors is equivalent to spending the day in darkness.

By reducing our exposure to bright natural light and true darkness, melatonin secretion and the body temperature rhythm are altered, which can disturb sleep. Consequently, increased exposure to sunlight at certain times of the day can minimize sleep-onset insomnia and early morning awakenings. Sleep-onset insomnia is characterized by a body temperature rhythm that falls too late at night. Because sunlight causes body temperature to rise, sleep-onset insomniacs can cause their body temperature to rise earlier and fall earlier, and therefore fall asleep more easily, by increasing exposure to early morning sunlight.

In contrast to sleep-onset insomnia, individuals who experience early morning awakenings often exhibit a body temperature rhythm that rises too early in the morning. Several studies have shown that increasing exposure to evening bright light can minimize early morning awakenings by delaying the body temperature rhythm so that it doesn't rise as early in the morning.

If you can't increase your exposure to natural bright light, consider purchasing a bright light box. They are relatively inexpensive, can be purchased on the internet and can be used while watching television or reading the newspaper.

References
 
1. Gregg D. Jacobs, Say Good Night to Insomnia. New York: Henry Holt, 1999.