Circadian activity rhythm disturbances predict mortality

Abstract

Introduction Sleep and circadian rhythm changes occur during aging, and have been associated with adverse health consequences and mortality. Previous studies investigating sleep and mortality focused mainly on sleep duration and suggest that the relation between sleep duration and mortality is U-shaped. It is still unclear if other sleep characteristics and if stability and fragmentation of the circadian rhythm predict mortality. Materials and methods Actigraphy and a sleep diary were used to measure the circadian activity rhythm and sleep in 1734 middle-aged and elderly participants of the Rotterdam Study. Circadian rhythm was measured with actigraphy to calculate the interdaily stability and intradaily variability (i.e. fragmentation) of the activity rhythm. Sleep was assessed objectively with actigraphy, and subjectively with a sleep diary to estimate sleep duration, sleep onset latency and wake after sleep onset. Sleep quality was measured with the Pittsburgh Sleep Quality Index. All- cause mortality was assessed by death certificates and records of general practitioners and hospitals. The association between circadian rhythm, sleep and mortality was estimated with cox proportional hazard models. Results The mean follow-up time was 5.9 years, in total, 137 deaths (7.9%) occurred. Higher stability of the circadian activity rhythm was associated with a lower mortality risk (HR = 0.82, 95% CI = 0.71–0.96) and more fragmentation to a higher mortality risk (HR = 1.25, 95% CI = 1.07–1.45) after adjustment for confounders. Whether assessed objectively or subjectively, sleep was not related to mortality in our study. Conclusion Lower stability and higher fragmentation of the circadian activity rhythm is related to higher all-cause mortality in a middle-aged and elderly population. Loss of circadian rhythm might be a disease indicator or a parameter for aging. Future research must show if stabilizing the circadian rhythm can improve quality of life and survival. Acknowledgements L.A. Zuurbier and A.I. Luik were supported by a Netherlands Organization for Scientific Research grant (NWO-VIDI: 017.106.370) awarded to H. Tiemeier.