Sex and the Clock: Exploring Sex Differences in Chronotype and Circadian Preferences Among Cognitively Healthy Older Adults.

This study aimed to compare objective circadian rest-activity-rhythm (RAR) measures with self-reported circadian behavior and morning-evening preference in cognitively healthy older men and women. A total of 129 participants (ages 65-90) completed the Horne & Ostberg Morning-Eveningness Questionnaire (MEQ) and the Circadian Type Inventory (CTI) to assess their morning-evening preference and circadian traits, including rigidity, vigor, languidness, and flexibility. These subjective measures were compared to objective actigraphy data from a sub-cohort of 70 individuals who wore actigraphy watches for 24 hours a day over a 7-day period. Rest-activity rhythm variables were derived from the actigraphy data and analyzed. The results revealed sex differences in circadian behavior. Languid and flexible men (higher CTI scores) had significantly higher depression scores (GDS, p = 0.045) and showed more evening preference (MEQ, p = 0.007) compared to their vigorous and rigid counterparts, while no significant differences were found in women. Actigraphy data showed that men had less stable (interdaily stability, IS, p = 0.030) and more fragmented (interdaily variability, IV, p = 0.001) circadian rhythms than women. A significant association was found between acrophase time and CTI-FR scores (β = -0.406, p < 0.001), with earlier acrophase times linked to more rigid circadian rhythms. Additionally, earlier acrophase times and morningness preference were associated with faster information processing speeds (IPS, p = 0.018). These findings suggest that circadian behaviors and their impact on mood and cognition are more pronounced in older men than women, highlighting the value of actigraphy in assessing circadian profiles and sex differences in aging.