AGING, RHYTHMS OF PHYSICAL PERFORMANCE, AND ADJUSTMENT TO CHANGES IN THE SLEEP-ACTIVITY CYCLE

Objectives-Shiftwork causes disturbances of the normal sleep-wake cycl e and circadian rhythm. There is concern that aging workers have more problems than younger counterparts when the human body clock is disrup ted. This review considers issues relating to aging, the circadian bod y clock, and adjustment to altered sleep-wake schedules. Methods-Repor ts on effects of aging on the human body clock were reviewed. Research concerned with adjustment to circadian phase shifts (as occurs in nig ht work) was considered. Results-With aging there is an increased tend ency towards morningness which is linked with difficulties in sleeping . The peak time and amplitude of normal circadian rhythms are altered. Tolerance of shiftwork can be linked with social factors as well as a daptation of the body clock. Conclusions-People habituated to night wo rk seem to have developed mechanisms which allow them to cope with dis ruptions to lifestyle and the endogenous body clock. Elderly people ar e more suited to phase advances, as occur in morning workshifts, than to phase delays such as nocturnal work.