RELATIONSHIPS BETWEEN SLEEP AND BODY-TEMPERATURE IN MIDDLE-AGED AND OLDER SUBJECTS

OBJECTIVES: Although changes in the circadian timing system are though t to be a major factor in the decline of sleep quality that often acco mpanies aging, few reports have actually examined this relationship in detail. Because some treatments for age-related insomnia are based on putative circadian changes, it is important to expand the limited dat abase that specifically addresses this issue. This study examined age- related changes in sleep, and relationships between those sleep change s and alterations in the circadian timing system, in a group of middle -aged and older subjects. DESIGN: Sixty healthy men and women between the ages of 40 and 84 were studied. A subset of older subjects (< 65 y ears) had reported sleep disturbance for at least 1 year before partic ipation. Polysomnography was obtained, and body core temperature was r ecorded continuously for 24 hours. All recordings took place in the La boratory of Human Chronobiology, Department of Psychiatry, Cornell Uni versity Medical College. RESULTS: There were no differences in sleep q uality between middle-aged and non-sleep-disturbed older subjects. How ever, timing of the minimum body temperature was earlier in the older non-sleep-disturbed subjects than in the middle-aged group. In contras t, sleep-disturbed older people had shorter total sleep times, reduced sleep efficiency, more waking time after sleep onset, and a reduced p roportion of REM sleep compared with non-sleep-disturbed older subject s. Yet, there were no differences between the two Older groups in the rhythm of body temperature. For the entire group, age was correlated n egatively with total sleep time, sleep efficiency, percentage of stage 2 sleep, and the timing of the temperature minimum. CONCLUSION: The r esults support the widely held notion that sleep and circadian rhythm changes occur with aging. However, the hypothesis that age-related cha nges in sleep may be associated with aging of the circadian system was supported only to a limited degree, suggesting that age-related sleep disturbance is likely to have multiple causes. Thus, treatment strate gies that incorporate a combination of interventions may be the most e ffective.