Associations Between Sleep And Cognition Among Middle-Aged And Older Adults In Europe

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Abstract Background The Survey of Health, Ageing and Retirement in Europe (SHARE) is a supranational longitudinal study of community-dwelling middle-aged and older adults involving 29 countries, including all continental members of the European Union. We analysed wave 8 of SHARE (2019/2020) for associations between sleep and cognition. Methods The previously validated SHARE Cognitive Instrument (SHARE-Cog), which includes 10-word registration, verbal fluency and 10-word recall, was used to assess cognition. Together with data on impairment in activities of daily living and subjective perception of cognition, participants were divided into four groups: dementia, mild cognitive impairment (MCI), subjective memory complaint (SMC), normal cognition (NC). Survey-weighted generalised linear regression models were used to compare groups. To analyse the association between sleep duration and cognition, total hours of sleep was plotted on the x-axis and mean SHARE-Cog score on the y-axis. Results 29,450 were included (55% female; mean age 68.27), categorised as: Dementia 4%, MCI 9%, SMC 14% and NC 73%. A characteristic ‘inverted U’ shaped association was observed between sleep duration and cognition. Compared to optimal sleep duration of seven hours, mean SHARE-Cog scores declined progressively with more or less sleep. Those with cognitive impairment were significantly more likely to report recent trouble sleeping: Dementia 47%; MCI 43%; SMC 46%; NC 30% (p <0.001). Cognitive impairment was also significantly associated with increased use of medication to aid sleep (Dementia 17%; MCI 13%; SMC 8%; NC 4%, p <0.001) and with daytime napping or resting (Dementia 72%; MCI 60%; SMC 45%; NC 41%, p <0.001). Conclusion This analysis of a large population-based study confirmed an ‘inverted-U’ shaped association between sleep duration and cognition. Cognitive impairment was also significantly associated with increased reports of recent trouble sleeping, increased use of medication to aid sleep, and increased daytime napping or resting.