What sleep characteristics predict cognitive decline in the elderly?

Background: Sleep is critical for optimal cognitive function, but as we age both cognitive impairment and sleep problems increase. Longitudinal, population-based studies can be used to investigate temporal relationships between sleep and cognition. Methods: A total of 2012 cognitively unimpaired individuals 65 years and over were drawn from the MRC Cognitive Function and Ageing Study (CFAS). They answered self-reported measures including: insomnia symptoms and age of onset, night time wakings, snoring, sleep onset latency, napping, daytime sleepiness and duration of night time sleep. Cognition was measured via the Mini-Mental State Examination. Results: It was found that daytime napping at baseline was associated with a lower risk of cognitive decline at two and 10 years, and that obtaining <= 6.5 h of night-time sleep and excessive daytime sleepiness at baseline were associated with an increased risk at 10 years. Conclusions: Daytime napping, night-time sleep duration, and excessive daytime sleepiness may be modifiable behaviours open to intervention strategies, or, clinical indicators of future decline in older individuals. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.