Objective Sleep and Circadian Rest‐Activity Rhythms and Multiple Domains of Cognitive Function in Older Men and Women

Abstract

AbstractBackgroundEmerging evidence from experimental and epidemiologic studies suggests that sleep and circadian rest‐activity rhythms (RAR) play a key role in dementia and Alzheimer Disease (AD) pathology. Studies with objective measures of sleep and RAR and multiple domains of cognition in older adults remain limited.MethodWe studied 820 older men and women enrolled in the Study of Muscle, Mobility, and Aging (SOMMA), a unique cohort designed to study the cellular biology of aging and related loss of mobility. In this initial cross‐sectional analysis, participants wore wrist actigraphs for a mean of 8.0 consecutive days; recordings were processed for traditional sleep‐wake measures including total sleep time (TST) and sleep efficiency (SE); as well as parametric (acrophase, pseudo‐F) and non‐parametric (interdaily stability [IS], intradaily variability [IV], and relative amplitude [RA]) 24‐hour RAR variables. Measures of cognitive function included global cognition (the Montreal Cognitive Assessment), executive function (Trails B test), memory (California Verbal Learning Test‐short form; and psychomotor performance (Digit‐Symbol Coding Test). In models adjusted for age, sex, clinic site and education, we examined adjusted mean cognitive test scores by quartiles or categories of sleep and RAR exposures.ResultMean age of the cohort was 76 years, 58% were female, and 15% were non‐white. Mean TST and SE were 6.9 hours and 85%, respectively. Higher RA, reflecting a more robust 24‐hour RAR, was associated with better cognition on all tests (p for trend <0.05). The association of higher pseudo‐F, a parametric measure or robustness of RAR, to cognition was limited to psychomotor performance (p<0.03). Better psychomotor performance was also related to higher IS (consistency of RAR across days); whereas those with delayed timing (acrophase) had worse psychomotor performance (p<.0006). Lower SE was related to worse cognitive function (psychomotor performance, global cognition, memory; p<.05). There were no associations between TST and any cognitive measures.ConclusionSE and RAR were variably associated with both global and specific domains of cognition in older men and women. The RA in particular was strongly related to multiple domains of cognition related to AD, and may be useful in identifying individuals at risk. Additional analyses will explore gender differences and longitudinal associations.