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Abstract Introduction Circadian rest/activity rhythms (RARs) are associated with cognitive function among older adults. Reports of poor cognitive function are common among individuals with insomnia. We examined the association of circadian RARs with performance in multiple cognitive domains among older adults with insomnia. Methods Older adults with insomnia were recruited from a tertiary academic medical center. Participants wore an actigraph and completed concurrent sleep diaries for up to 14 days. We derived nonparametric circadian RARs including relative amplitude (RA), interdaily stability (IS), intradaily variability (IV), maximum ten-hour activity (M10) and minimum five-hour activity (L5). Secondary parametric RARs included amplitude, acrophase, and midline statistics of rhythm (MESOR). Cognitive function was measured via the Brief Test of Adult Cognition by Telephone as well as in-home computerized administration of the psychomotor vigilance test, Stroop Test, and a Task-switching test. Cognitive testing results were grouped into eight a priori-defined domains (attention, inhibition, cognitive flexibility, episodic verbal memory, working memory, reasoning, executive function, processing speed). Composite domain scores were calculated by averaging the z-scores for all individual tests within that domain. Finally, a series of 64 linear regression models were tested to determine the association between circadian RAR parameters and cognitive domains. All models were adjusted for age, sex, education, and total sleep time. We used the Benjamini-Hochberg procedure for correcting false discovery rate (BH-FDR) to correct for multiple comparisons. Results The final sample included 30 older adults with insomnia (67% women, mean age=68.0 SD 6.58 years) who self-identified as White (80%), Black (17%) and American Indian (7%) race. Greater IS (t=2.82, p=0.011), RA (t=2.59, p=0.018), and L5 (t = 2.61, p=0.017) were associated with greater cognitive flexibility. Of parametric RARs, greater amplitude (t = 2.53, p=0.020) and acrophase (t=2.67, p=0.015) were also associated with greater cognitive flexibility. No other significant associations were observed for any cognitive domain. Conclusion Circadian RARs were associated with cognitive flexibility but not other cognitive domains. These findings highlight the potential importance of circadian RAR parameters among older adults with insomnia and provide further support for cognitive flexibility as a key cognitive outcome among older adults with sleep problems. Support (if any) Merck Investigator Studies Program (#59170).
Pfaeffle et al. (Sat,) studied this question.