Circadian Changes - Aging And Energy: Chronic Fatigue

Content provided by the Faculty of the Harvard Medical School

Circadian changes

Although increased fatigue is not inevitable with increased age, there are certain age-related factors that make you feel weaker and, in general, less energetic. For one thing, your circadian cycle advances, making you want to fall asleep earlier at night and wake up earlier in the morning. Indeed, the most important influence on sleep rhythms is aging.

Insomnia becomes more common with age.

Insomnia becomes more common as people get older. For reasons that are not understood, older people spend less time in deep sleep, the type of sleep that is considered the most important for restoring your energy. With less deep sleep, you wake up more often in the middle of the night. And the more often you wake up at night, the less rested you feel the next day.

The amount of deep sleep that people get each night at age 30 is about half the amount they get at age 20. After age 30, the decrease in deep sleep and the increase in nighttime awakenings continue. Not only do people wake up more often in middle age, it takes longer to fall back to sleep. By age 65, people spend less than 5% of sleep time in deep sleep, compared with about 20% when they were in their 20s. In addition, melatonin levels decline with age and virtually disappear by old age. Because melatonin helps you feel sleepy at night, its decline can make it harder to fall asleep. The reductions in melatonin and in deep sleep help explain why insomnia becomes more common with age.

As you get older, you're more likely to make up for your nighttime sleep deficit by napping. But napping can make insomnia worse by keeping you from feeling tired enough at bedtime.

Last updated:	January 23, 2007