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ABSTRACT
Biological evidence suggests that ethno-racial differences in morning–evening type are possible, whereby Blacks may be more likely to be morning type compared to Whites. However, population-level evidence of ethno-racial difference in morning–evening type is limited. In an earlier study, we reported that morning type was more prevalent in Blacks compared to Whites in the United Kingdom (UK) Biobank cohort (N = 439 933). This study aimed to determine if these ethno-racial differences persisted after accounting for an even broader range of social, environmental and individual characteristics and employing an analytic approach that simulates randomization in observational data, propensity score modeling. Data from UK Biobank participants whose self-identified race/ethnicity was Black/Black British or White; who did not report daytime napping, shift work or night shift work; who provided full mental health information; and who were identified using propensity score matching were used (N = 2044). Each sample was strongly matched across all social, environmental and individual characteristics as indicated by absolute standardized mean differences <0.09 for all variables. The prevalence of reporting nocturnal short, adequate and long sleep as well as morning, intermediate and evening type among Blacks (n = 1022) was compared with a matched sample of Whites (n = 1022) using multinomial logistic regression models. Blacks had a 62% greater odds of being morning type [odds ratio (OR) = 1.620, 95% confidence interval (CI): 1.336–1.964, p < .0001] and a more than threefold greater odds of reporting nocturnal short sleep (OR = 3.453, 95% CI: 2.846–4.190, p < .0001) than Whites. These data indicate that the greater prevalence of morning type and short nocturnal sleep in Blacks compared to Whites is not fully explained by a wide range of social and environmental factors. If sleep is an upstream determinant of health, these data suggest that ethno-racially targeted public health sleep intervention strategies are needed.
Declaration of interest
The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.
Funding
This research was conducted using the UK Biobank Resource (application 3474). This work was supported by the Robert Wood Johnson Health and Society Scholars program at the University of Pennsylvania under grant number 69251 (AH), the National Institutes of Health under grant T32 HL 7953 (SKM), the Institutional Development Award (IDeA) Center of Biomedical Research Excellence from the National Institute of General Medical Sciences of the National Institutes of Health under grant number P20GM113125 (FP), the University of Pennsylvania’s University Research Foundation (AH) and the University of Delaware’s Research Foundation (FP).