The association between sleep and cognitive pre‐frailty in community‐dwelling older adults: A two‐year cohort study

Abstract

AbstractBackgroundSleep has been related to cognition and frailty, respectively. Cognitive frailty, the co‐existence of mild cognitive impairment (MCI) and physical frailty, has been proposed in 2013 and its relation with sleep remains unclear. To predict cognitive frailty in the preclinical stage, this study aimed to explore the relationship between sleep and cognitive pre‐frailty in non‐demented older adults.MethodThis study is part of the ongoing Taiwan Initiative for Geriatric Epidemiological Research. After exclusion of participants with specific conditions and loss to follow‐up, 324 older adults from the senior health checkup program of National Taiwan University Hospital were included at baseline (2015‐2017). Outcome of this study was the coexistence of MCI and pre‐frailty (cognitive pre‐frailty) and were assessed at baseline and two‐year follow‐up (2017‐2019). Global and domain‐specific cognition were assessed by Taiwanese version of Montreal Cognitive Assessment and a battery of neuropsychological tests, respectively. Pre‐frailty was defined as the existence of one or two out of five conditions using modified Fried’s frailty phenotype. Sleep variables was available at baseline, which included global sleep quality [assessed by Pittsburgh Sleep Quality Index (PSQI), score range: 0‐21)], sleep duration (in hours), and daytime sleepiness (assessed by Epworth Sleepiness Scale, ESS, score range: 0‐24). Generalized linear mixed model was utilized to assess the association between sleep and cognitive pre‐frailty over 2 years adjusting for age, sex, years of education and other important covariates.ResultParticipants’ mean age was 75.2 years at baseline. Prevalence of cognitive pre‐frailty was 1.85% at baseline and 2.55% at two‐year follow‐up. Instead of a linear relationship, we found a non‐linear association between sleep and cognition. When mean PSQI score and mean sleep duration deviated from the corresponding sample mean (PSQI score: 6.3; sleep duration: 6.2 hours), the severity of cognitive pre‐frailty increased [quadratic PSQI score: adjusted odds ratio (aOR)=1.02, 95% confidence interval (CI)=0.01‐0.04; quadratic sleep duration: aOR=1.15, 95% CI=0.04‐0.23]. No significant association was found between daytime sleepiness and cognitive pre‐frailty.ConclusionThis study found a nonlinear association of global sleep quality and sleep duration with cognitive pre‐frailty over two years in the community‐dwelling older adults.