OBJECTIVE:To examine rest-activity circadian rhythm (RAR) and cognitive decline in older men. DESIGN:Longitudinal. SETTING:Osteoporotic Fractures in Men (MrOS) and ancillary Outcomes of Sleep Disorders in Men (MrOS Sleep) studies. PARTICIPANTS:MrOS and MrOS Sleep participants (N=2,754; mean age 76.0 ± 5.3). MEASUREMENTS:The Modified Mini-Mental State examination (3MS) was used to assess cognition at baseline (2003-05) and follow-up examinations (2005-06 and 2007-09). Wrist actigraphy was used to measure 24-hour activity counts at baseline. RAR variables included amplitude (strength of activity rhythm), mesor (mean activity level), pseudo F-statistic (overall circadian rhythm robustness), and acrophase (time of daily peak activity). RESULTS:After an average of 3.4 ± 0.5 years, men with lower amplitudes, mesors, and pseudo F-statistics had greater decline in 3MS performance (amplitude: -0.7 points Q1 vs -0.5 points Q4, p<.001; mesor: -0.5 points Q1 vs -0.2 points Q4, p=.01; pseudo F-statistic: -0.5 points Q1 vs -0.3 points Q4, p<.001). Lower amplitudes and pseudo-F statistics were associated with greater odds of clinically significant cognitive decline (≥5-point decrease) (amplitude Q1 vs. Q4: odds ratio (OR)=1.4, 95% confidence interval (CI)=1.0-1.9; pseudo-F statistic Q1 vs Q4: OR=1.4, 95% CI=1.0-1.9). Men with phase-advanced acrophase had greater odds of clinically significant cognitive decline (OR=1.8, 95% CI=1.2-2.8). Results were adjusted for multiple confounders. CONCLUSION:Several parameters of disrupted RAR (lower amplitude, pseudo F-statistic, mesor, phase-advanced acrophase) were associated with greater cognitive decline in older community-dwelling men. These findings contribute to a growing body of evidence suggesting that altered RARs are associated with cognitive decline in older adults. J Am Geriatr Soc 66:2136-2143, 2018
