Circadian Rhythms and Aging

As we age, our circadian rhythms or biologic clocks advance resulting in the "early to bed-early to rise" pattern in which an older persons gets sleepy early in the evening and then wakes up at 3:00 in the morning. This pattern is called advanced sleep phase syndrome. The sleep rhythm is shifted forward so that 7 or 8 hours of sleep are still obtained but the individuals will wake up extremely early because they have gone to sleep quite early.

Other changes in circadian rhythms are associated with more awakenings during the night and this results in more naps being taken during the day. Older adults also have more difficulty with jet lag when changing time zones. This can cause an individual to get far less sleep than is needed because his body will still wake up as if he were in the old time zone.

These changes in circadian rhythms may occur for several reasons, including aging itself. However, it appears that light is the strongest cue for circadian rhythms and many older adults may not receive sufficient light exposure. As we age, we may spend less time outdoors or eye diseases, such as cataracts, may block out the light needed to maintain sleep patterns. About 2 hours of bright light exposure are needed each day to synchronize circadian rhythms.

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