Perils of the nighttime: impact of behavioral timing and preference on mental and physical health in 73,888 community-dwelling adults

Importance Human mental and physical health is influenced by both the inclination to sleep at specific times (chronotype) as well as the actual sleep timing (behavior). How the alignment between these impacts mental and physical health has not been well described. Objective The goal of this study is to examine the impact of chronotype, actual timing of behavior, and the alignment between the two on a variety of mental and physical health outcomes. Design A cohort analysis of the UK Biobank (2006 to Current). Setting Outpatient. Participants Community-dwelling adults (n=73,888). Exposure Ad libitum behavior for one week. Main Outcome(s) and Measure(s) Sleep time preference (chronotype), one week of wrist-worn accelerometry (actigraphy), and demographic variables were collected. Actigraphy was analyzed using non-parametric methods to determine the actual timing of behavior. Prevalence and likelihood (odds-ratios) of developing mental health disorders (mental, behavioral, and neurodevelopmental disorders, generalized anxiety disorder, depression) and physical health disorders (including metabolic disorder, diabetes, obesity, hypertension, circulatory disorder, digestive disorder, respiratory disorder, and all-cause cancer) were calculated and corrected for common demographic variables (sex, age, body mass index, material deprivation, sleep duration). Results Our final sample was 56% female, 63.5 [56.3 - 68.6] years in age, with a Body Mass Index of 26.0 [23.6 - 29.0], Townsend Deprivation Indices of −2.45 [−3.82 - −0.17], and self-reported sleep duration of 7 [6 - 8] hours. As compared to morning-types with early behavior (aligned), morning-types with late behavior (misaligned) had an increased risk of both mental (OR=1.52±0.06, p<0.001) and physical (OR=1.45±0.03, p<0.001) health disorders. As compared to evening-types with late behavior (aligned), however, evening-types with early behavior (misaligned) had a decreased risk of both mental (OR=0.85±0.06, p=0.002) and physical (OR=0.66±0.03, p<0.001) disorders. Conclusion/Relevance Despite potential misalignment between sleep and circadian rhythms, going to sleep late is associated with worse mental and physical health in both morning- and evening-types.