24‐hour rest‐activity rhythms and light exposure patterns in relation to cognitive function in a nationally representative U.S. sample

Abstract

AbstractBackgroundHuman diurnal behaviors are orchestrated by the internal circadian clock and influenced by external stimuli such as light. Aging is associated with declined circadian output and shifted circadian phase, leading to weakened rest‐activity rhythms and altered light exposure patterns, which may in turn further exacerbate circadian impairment. Limited but growing research reported that characteristics of rest‐activity rhythms were associated with risk of dementia and cognitive decline in older populations. However, there are several gaps in the literature: 1) most previous studies included predominantly white participants with relatively high socioeconomic status, limiting the generalizability of study findings to more diverse populations; 2) few studies examined the 24‐hour light exposure pattern, an environmental cue essential to healthy circadian function, in relation to cognitive function.MethodsWe applied the extended cosine model, nonparametric algorithms, and functional principal component analysis (fPCA), to characterize rest‐activity rhythms and light exposure patterns in the National Health and Nutrition Examination Survey (2011‐2014). Cognitive function was measured by word learning and recall modules from the Consortium to Establish a Registry for Alzheimer’s disease (CERAD), the Animal Fluency test, and the Digit Symbol Substitution test.ResultsMultiple rest‐activity characteristics were associated with different aspects of cognitive function, generally supporting a relationship between weakened circadian rhythms and poorer cognitive performance. For example, when compared to the highest quintile, the lowest quintile of F statistic, a measure of overall rhythmicity, was associated with a significantly lower score on the CERAD delay recall test (beta (95% confidence interval (CI)), ‐0.61 (‐0.77, ‐0.18)) and an increase in the odds of having a performance score in the lowest quartile of the study sample (odds ratio (95% CI), 1.55 (1.05, 2.29)). Moreover, measures of amplitude and rhythm fragmentation derived from nonparametric algorithms and fPCA were also associated with cognitive function. Findings were generally consistent across subgroups with different gender, age, race/ethnicity and education levels, but subgroup differences were also observed. Moreover, preliminary findings suggested a relationship between light exposure patterns and cognitive function.Conclusions24‐hour rest‐activity and light exposure patterns are associated with cognitive function in a diverse and nationally representative sample.