Objective: To measure the influence of age on measures of nocturnal activity and immobility in 100 healthy subjects aged 50 to 98 years.
Design: Cross-sectional study.
Setting: Urban population in Leiden. Recordings were performed at home while the subjects maintained their habitual 24-hour pattern of activities.
Participants: 100 subjects without a history of major medical disorders and a normal neurological examination and performance-oriented assessment of gait (Tinetti).
Measurements: Motor activity was recorded during six successive nights with a wrist-worn activity monitor. The occurrence of supra-threshold motor activity was recorded over 15-second epochs. A questionnaire was used to evaluate sleep habits and the occurrence of sleep disturbances. Four mean measures reflecting activity or immobility during the nocturnal period were calculated for each subject.
Results: Only one out of four measures, (ie, the nocturnal proportion of time with movement, increased with age for females. For males, no age effects emerged. The mean duration of nocturnal immobility periods was higher in females than in males. Also, for females, the use of hypnotics increased with successive decades. Sex and the use of hypnotics were significantly related to the mean duration of immobility periods.
Conclusion: If care is taken not to confound aging with illness, measures of nocturnal activity and immobility reveal only marginal effects of aging.