Sleep habits are associated with cognition decline in physically robust, but not in frail participants: a longitudinal observational study.

Frail older adults are vulnerable to stressors; thus, sleep related cognition impairment might more greatly affect frail than healthy older adults. In the present study, we investigated whether the association between sleep problems and cognition varies with physical frailty status (modified from Fried et al.). Participants 55 years and older who completed a baseline and follow-up questionnaire (median follow-up: 5.5 years), were included in the analysis. Sleep parameters were evaluated in an interview at the baseline. Cognitive decline was defined as a loss of 3 or more points on the Mini-Mental State Examination (MMSE) at follow-up. Associations between sleep problems and cognitive decline were examined using logistic regression and were stratified by baseline physical frailty status, adjusted for potential confounders. A short total sleep duration (< 5 vs. 7-9 h, odds ratio (OR) = 1.88, 95% confidence interval (CI) 1.18-3.00), excessive daytime sleepiness (OR = 1.49, 95% CI 1.04-2.13), low sleep efficiency (< 65% vs. ≥ 85%, OR = 1.62, 95% CI 1.07-2.46), and insomnia complaints (OR = 2.34, 95% CI 1.23-4.43) were associated with MMSE decline in physically robust. The association was stronger for the sleep summary score, which summarized abnormal sleep duration, excessive daytime sleepiness, and insomnia complaints ([Formula: see text] 2 vs. 0, OR = 3.79, 95% CI 2.10-6.85, p < 0.0001). Due to the low prevalence of frailty in this community-dwelling population, the statistical power to detect an association was low. More evidence is needed to clarify the role of sleep in the progression of cognitive decline in frail individuals.