Rest‐Activity Rhythms and Cognitive Decline in Older Men: The Osteoporotic Fractures in Men Sleep Study

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