REST/ACTIVITY RHYTHMS AND MORTALITY RATES IN OLDER MEN: MROS SLEEP STUDY

An association between increased risk of mortality and disruptions in rest/activity circadian rhythms (RAR) has been shown among adults with dementia and with metastatic colorectal cancer. However, the association among a more general population of older adults has not been studied. Our study population consisted of 2964 men aged >= 67 yrs of age enrolled in the Outcomes of Sleep Disorders in Older Men (MrOS Sleep) Study. Rest/activity patterns were measured with wrist actigraphy. RAR parameters were computed and expressed as quintiles, and included acrophase (time of peak activity level), amplitude (peak-to-nadir difference), mesor (middle of the peak), pseudo F-value (overall circadian rhythmicity), beta (steepness), and alpha (peak-to-trough width). After adjustment for multiple potential confounders, men in the lowest quintile of pseudo F-value had a 57% higher mortality rate (hazard ratio [HR] = 1.57, 95% CI, 1.03-2.39) than men in the highest quintile. This association was even stronger with increased risk of cardiovascular disease-related mortality (CVD) (HR = 2.32, 95% CI, 1.04-5.22). Additionally, men in the lowest quintile of acrophase had a 2.8-fold higher rate of CVD-related mortality (HR = 2.84, 95% CI, 1.29-6.24). There was no evidence of independent associations with amplitude, mesor, alpha, beta, and mortality risk. Older men with less robust RAR and earlier acrophase timing have modestly higher all-cause and CVD-related mortality rates. Further research should examine potential biological mechanisms underlying this association. (Author correspondence: ames0047@umn.edu).