Sex Differences in the Association Between 24-hour Rest-Activity Rhythms and Frailty Among U.S. Older Adults: Findings from NHANES 2011-2014.

Background: Little is known as to how rest-activity rhythms (RAR) are associated with frailty and how this relationship differs by sex. This study examined the relationship between RAR and frailty in a nationally representative sample of US older adults, focusing on the moderating role of sex.

Methods: 2,531 participants aged ≥60yrs [Females:55.2%; Frail:5.15% (4.02-6.29); Pre-frail:33.49% (31.29-35.68)] were included using the 2011-2014 National Health and Nutrition Examination Survey. Non-parametric RAR parameters, including inter-daily stability (IS), intra-daily variability (IV), relative amplitude (RA), most active 10-h, and least active 5-h, were estimated from wrist-worn actigraphy data. Frailty status was assessed using a modified version of frailty phenotype (range:0-5): frail (≥3), pre-frail (1-2), and non-frail (0). Multinomial logistic regression models were used to examine the interest of associations, adjusting for potential confounders.

Results: Frail and pre-frail older adults exhibited significantly lower RA, IS, higher IV, and phase delay when compared to non-frail older adults (p's<.05). Particularly, older adults with low RA had significantly greater odds of being frail and pre-frail [aOR(95%CIs); Frailty:5.60(2.61-12.04); Pre-frailty:1.58(1.13-2.20)]. Significant sex-interaction was observed (p<.01), with this association being greater in females than in males [aOR(95%CIs); Females:7.78(2.98-20.30) for frailty, 2.31(1.60-3.32) for pre-frailty; Males:4.48(1.38-14.54) for frailty, 1.12(0.61-2.07) for pre-frailty].

Conclusion: Weakened RAR strength is unfavorably associated with frailty, particularly in females. RAR may be a useful indicator associated with frailty in older adults, but sex-specific differences should be considered. Further longitudinal research is necessary to investigate the bidirectionality of their association.