Associations between sleep and cognition among middle-aged and older adults in Europe

BackgroundThe Survey of Health, Ageing and Retirement in Europe (SHARE) is a longitudinal multi-country study of community-dwelling middle-aged and older adults including data on sleep and cognition.ObjectiveTo examine the cross-sectional association between sleep-related issues and cognition in the SHARE (pooling waves 8 and 9; 2019-2022).MethodsSubjective sleep data were obtained from SHARE waves 8 and 9. Objective data were available from wave 8. The SHARE Cognitive Instrument (SHARE-Cog) assessed cognition. Participants were divided into three groups: probable dementia, cognitive impairment no dementia (CIND), and normal cognition (NC). Survey-weighted generalized linear regression models were used to compare groups.Results88,889 interviews were included (55% females; mean age 68.88), categorized as: probable dementia 7%, CIND 12%, and NC 81%. While, in the unadjusted analysis, a characteristic 'inverted U' shaped association was observed between sleep duration and cognition, only the association between cognition and longer sleep durations ≥10 hours remained statistically significant after adjusting for potential confounders. Cognitive impairment was significantly associated with subjective reports of recent trouble sleeping, weekly use of medication to aid sleep, and daytime napping, although only the association with daytime napping remained statistically significant after adjusting for potential confounders.ConclusionsThis analysis confirmed an association between sleep duration ≥10 hours and lower cognitive scores among community-dwelling middle-aged and older Europeans. Cognitive impairment was also significantly associated with daytime napping. Further research is required to understand the clinical significance of these findings and establish the underlying causal relationships.