Assessment of sleep and circadian rhythm disorders in the very old: the Newcastle 85+ Cohort Study.

Objectives: to examine the association between subjective and objective measures of sleep and wake and other health parameters in a cohort of the very old.

Design: a population-based cohort study.

Setting: primary care, North East England.

Participants: four hundred and twenty-one men and women, aged 87-89, recruited to the Newcastle 85+ Study cohort.

Methods: sleep questionnaires were administered and sleep-wake patterns were assessed over 5-7 days with a novel wrist triaxial accelerometer. Associations between sleep measures and various health parameters, including mortality at 24 months, were examined.

Results: only 16% of participants perceived their sleep as severely disturbed as assessed with questionnaire responses. Wrist accelerometry showed marked variation between normal and abnormal sleep-wake cycles that did not correlate with the participants' perception of sleep. Impaired sleep-wake cycles were significantly associated with cognitive impairment, disability, depression, increased falls, body mass index and arthritis but not with any other specific disease markers and with decreased survival.

Conclusions: commonly used sleep questionnaires do not differentiate well between those with objectively determined disturbance of sleep-wake cycles and those with normal cycles. Abnormal sleep-wake patterns are associated with institutionalisation, cognitive impairment, disability, depression and arthritis but not with other diseases; there is also an association with reduced survival.