Circadian characteristics of sleep propensity function in healthy elderly: a comparison with young adults

Changes in sleep-wake patterns are among the hallmarks of biological aging, Elderly persons complain of daytime drowsiness and difficulties in initiating and maintaining sleep. The question of whether age-related changes in sleep-wake distribution are the result of a dimunition in amplitude of the endogenous circadian pacemaker, resulting in a decline in nocturnal sleep tendency and an increase in diurnal sleep tendency, or a manifestation of the impact of the medical and psychosocial burden on sleep has not yet been fully determined. In the present study, we utilized a 7/13 ultrashort sleep-wake paradigm to investigate the 24-hour sleep propensity function (SPF) in healthy elderly persons. Seventeen healthy, elderly males, aged 65-78 years, and eight young males, aged 19-26, participated in the study. All elderly subjects were living independently in the community and were vigorous, physically active, and socially engaged. The young adult subjects were students living on campus, all with the same daily schedule. As anticipated, polysomnographic measures from the night prior to experimental periods differed between the elderly and young subjects. Specifically, the elderly had a reduction in percentage of sleep stage 3/4 and in sleep efficiency. The results of the 7/13 ultrashort sleep-wake paradigm showed that although aging did not affect the overall structure of the SPF, there was an age-related trend toward lower circadian amplitude and advanced phase. Our findings suggest that these age-related changes in sleep propensity may contribute to the difficulties in initiating sleep and to the early morning awakening.