Circadian rest-activity rhythms in demented and nondemented older community residents and their caregivers.

OBJECTIVE: Disruptive nocturnal behaviors (DNBs) of older people often threaten the caregiving arrangements on which their community tenure depends. Dementing disorders are especially prone to result in disrupted sleep and agitated behaviors ("sundowning"). The objective here was to develop an objective correlate of DNBs, by which their severity and effects on caregivers can be measured.
DESIGN: Quantitative comparison of subjective sleep and motor activity patterns in older people and their caregivers. It was hypothesized that older people with reported DNBs would be more motorically active at night than their caregivers.
SETTING: Subjects' homes. PARTICIPANTS: Twenty-five demented and 18 nondemented older day-care participants and their paired caregivers. MEASUREMENTS: Older subjects and caregivers simultaneously kept daily sleep logs and recorded wrist motor activity every .5 minute for 9 days. A novel method was devised to identify and exclude from analysis periods when the activity monitor was not being worn. Such periods were common. Activity data were analyzed by computing hourly means and by fitting cosine models by least squares.
RESULTS: Demented older people were not significantly more active at night than their caregivers, though group differences varied by time of night. They were significantly less active in the daytime than were their caregivers. Nondemented older people were significantly more active at night than their caregivers and were as active by day as their caregivers. The caregivers of demented and nondemented older people had similar rest-activity patterns. The mean amplitudes of cosine models were smaller in the older adults. Acrophases (peaks) fell between 2 and 3 pm and did not differ significantly among the groups.
CONCLUSIONS: As a result of increased nighttime motor activity and decreased daytime activity, rest-activity rhythms were flatter in older adults than in caregivers. This was not explained fully by age and does not necessarily imply that the output of a circadian pacemaker was low. Decreased daytime activity may have resulted from deficient physical stimulation or frailty. Frailty may also explain why nighttime activity was not more elevated in the demented older people. Increased nighttime activity is probably explained by depression, sleep-schedule disturbances, restless legs, or other sleep disorders. Judging by their shared variations of activity, caregivers interacted mainly with the demented older people at bedtime and at rising time in the morning.