Association between circadian rhythms, sleep and cognitive impairment in healthy older adults: an actigraphic study.

There is increasing evidence for the relationship between circadian rhythm disturbance and cognitive decline in the older adult. This study measured circadian activity rhythms in a small group of healthy community-dwelling older adults (n = 26). Each participant completed a battery of neuropsychological tests and completed sleep diaries and 6 days of actigraphy. Ten participants were identified as having very early signs of cognitive decline as indicated by their performance on the memory tests. Results showed minimal differences on the sleep/activity and circadian parameters across the two groups (declined vs. intact), although there was a significant difference in the acrophase between the declined and intact groups. These findings, although exploratory, suggest that very subtle changes in circadian rhythm may be detected in older adults showing pre-clinical changes in cognitive performance.