Because the prevalence of several medical and psychiatric conditions that affect sleep, as well as the prevalence of specific sleep disorders, is high in the elderly population, it is extremely difficult to portray the picture of the “normal” elderly sleeper. Nevertheless, studies of age-related changes in sleep architecture have found some common characteristics. Sleep efficiency, defined as the amount of time asleep relative to the amount of time in bed, is decreased to 70% to 80%, compared to 90% or more in younger adults. Total sleep time is reduced, particularly in the later part of the sleep episode. The amount of stage 1 sleep, which is the transitional state between wake and sleep, is increased, while the amount of stages 3 and 4 (also termed slow-wave sleep or delta sleep) is much decreased. Specifically, the amplitude of slow-wave activity is significantly reduced. Therefore, older people spend more of the night in light sleep and are more likely to arouse (awaken) in response to external stimuli during the night.

Changes in the amount of REM sleep and latency of REM (time from sleep onset to the first REM sleep period) in the elderly are controversial. While some studies report a reduction in the percentage of REM, others report few or no changes in REM with aging. Feinberg reported a shorter REM latency and longer duration of REM sleep in the first sleep cycle. Reynolds et al. reported a “flat” temporal distribution of REM, with no changes in the percentages of REM sleep throughout the night, unlike the increase in REM sleep in the second half of the night typically seen in young adults. Some studies have shown shorter REM latencies in the elderly; however, this may be due to the decrease in the amount of non-REM sleep in stages 3 and 4. Alternatively, as REM sleep is coupled to the circadian rhythm of core body temperature, which has been found to be phase advanced in the elderly population, it is possible that changes in circadian timing account for the reduced REM latency compared to young adults.

Studies looking at gender differences have shown that despite the tendency for women to complain about their sleep more often than men, older women sleep somewhat better than older men. This conclusion is consistent with polysomnographic findings showing that slow-wave sleep is more preserved in older women than it is in older men. Sleep maintenance, particularly in the last part of the night, was also reported to be poorer in older men than women. Although sleep disruption in elderly women may be milder compared to elderly men, women tend to report their sleep problems and seek help more often than their male counterparts.