Circadian rest-activity rhythms and cognitive decline and impairment in older Chinese adults: A multicohort study with prospective follow-up

Background: The associations between rest-activity rhythms and cognitive health are inconclusive. The potential changes in rest-activity rhythms in older people with mild cognitive impairment (MCI) remains unclear. This study aimed to examine the association between rest-activity rhythms and cognitive health across different outcome measures in older Chinese people.Methods: A total of 710 community-dwelling participants (average age 81.1 +/- 5.2 years) from two cohort studies. Wrist-worn accelerometer data was used to estimate the circadian rest-activity rhythms at baseline. Cognitive function was assessed and clinical diagnosis was made at baseline and follow-up. The two-way Analysis of Covariance was used to compare the differences in rest-activity rhythms across participants with cognitively normal, MCI and Alzheimer's disease (AD). Logistic regression models were used to investigate the association between rest-activity rhythms and incidence of cognitive decline and impairment in a 4-year prospective followup of cognitively normal individuals.Results: There was a progressive trend of lower relative amplitude and higher activity level during the least active 5 h across participants with cognitively normal, MCI and Alzheimer's disease (AD). Among the cognitively normal participants, lower relative amplitude at baseline was associated with a greater risk of cognitive decline (per 1 SD decrease, odds ratio 1.66 [95 %CI 1.13-2.45]) and increased incidence of MCI or AD (per 1 SD decrease, 1.68 [1.12-2.50]).Conclusions: Lower relative amplitude could potentially serve as a robust biomarker of cognitive decline and impairment. Further studies could evaluate the potential benefits of interventions associated with rest-activity relative amplitude to prevent or delay the progression of AD.