Association of sleep duration at age 50, 60, and 70 years with risk of multimorbidity in the UK: 25-year follow-up of the Whitehall II cohort study

Background Sleep duration has been shown to be associated with individual chronic diseases but its association with multimorbidity, common in older adults, remains poorly understood. We examined whether sleep duration is associated with incidence of a first chronic disease, subsequent multimorbidity and mortality using data spanning 25 years. Methods and findings Data were drawn from the prospective Whitehall II cohort study, established in 1985 on 10,308 persons employed in the London offices of the British civil service. Self-reported sleep duration was measured 6 times between 1985 and 2016, and data on sleep duration was extracted at age 50 (mean age (standard deviation) = 50.6 (2.6)), 60 (60.3 (2.2)), and 70 (69.2 (1.9)). Incidence of multimorbidity was defined as having 2 or more of 13 chronic diseases, follow-up up to March 2019. Cox regression, separate analyses at each age, was used to examine associations of sleep duration at age 50, 60, and 70 with incident multimorbidity. Multistate models were used to examine the association of sleep duration at age 50 with onset of a first chronic disease, progression to incident multimorbidity, and death. Analyses were adjusted for sociodemographic, behavioral, and health-related factors. A total of 7,864 (32.5% women) participants free of multimorbidity had data on sleep duration at age 50; 544 (6.9%) reported sleeping <= 5 hours, 2,562 (32.6%) 6 hours, 3,589 (45.6%) 7 hours, 1,092 (13.9%) 8 hours, and 77 (1.0%) >= 9 hours. Compared to 7-hour sleep, sleep duration <= 5 hours was associated with higher multimorbidity risk (hazard ratio: 1.30, 95% confidence interval = 1.12 to 1.50; p < 0.001). This was also the case for short sleep duration at age 60 (1.32, 1.13 to 1.55; p < 0.001) and 70 (1.40, 1.16 to 1.68; p < 0.001). Sleep duration >= 9 hours at age 60 (1.54, 1.15 to 2.06; p = 0.003) and 70 (1.51, 1.10 to 2.08; p = 0.01) but not 50 (1.39, 0.98 to 1.96; p = 0.07) was associated with incident multi-morbidity. Among 7,217 participants free of chronic disease at age 50 (mean follow-up = 25.2 years), 4,446 developed a first chronic disease, 2,297 progressed to multimorbidity, and 787 subsequently died. Compared to 7-hour sleep, sleeping.5 hours at age 50 was associated with an increased risk of a first chronic disease (1.20, 1.06 to 1.35; p = 0.003) and, among those who developed a first disease, with subsequent multimorbidity (1.21, 1.03 to 1.42; p = 0.02). Sleep duration.9 hours was not associated with these transitions. No association was found between sleep duration and mortality among those with existing chronic diseases. The study limitations include the small number of cases in the long sleep category, not allowing conclusions to be drawn for this category, the self-reported nature of sleep data, the potential for reverse causality that could arise from undiagnosed conditions at sleep measures, and the small proportion of non-white participants, limiting generalization of findings. Conclusions In this study, we observed short sleep duration to be associated with risk of chronic disease and subsequent multimorbidity but not with progression to death. There was no robust evidence of an increased risk of chronic disease among those with long sleep duration at age 50. Our findings suggest an association between short sleep duration and multimorbidity. Author summary Why was this study done? The prevalence of multimorbidity is on the rise as reflected in over half of older adults having at least 2 chronic diseases in high-income countries, making multimorbidity a major challenge for public health. Both short and long sleep duration has been shown to be associated with individual chronic diseases, but their associations with multimorbidity and subsequent mortality risk remain unclear. What did the researchers do and find? We used data on more than 7,000 men and women from the Whitehall II cohort study to extract sleep duration at age 50, 60, and 70 and examined its association with incident multimorbidity over 25 years of follow-up. Role of sleep duration at age 50 in transitions from a healthy state to a first chronic disease, multimorbidity, and mortality was also examined using a multistate model. We found a robust association of sleep duration.5 hours at age 50, 60, and 70 (separate analyses) with higher risk of incident multimorbidity, while the association with sleep duration.9 hours was observed only when measured at age 60 and 70. Analysis of transitions in health states showed short sleep duration at age 50 to be associated with 20% increased risk of a first chronic disease, and with a similar increased risk of subsequent multimorbidity, but within this framework there was no clear evidence of associations with mortality. There was no robust association between sleep duration >= 9 hours at age 50 and risk of 1 chronic disease or multimorbidity. However, in those with a chronic condition there was some evidence of higher risk of multimorbidity. What do these findings mean? Our comprehensive analyses of the association of sleep duration with multimorbidity and the natural course of chronic disease show short sleep duration to be associated with the onset of chronic disease and multimorbidity but not with subsequent mortality in those with chronic disease(s). There was no clear evidence for an association between long sleep duration at age 50 and risk of chronic disease. Rather the increased risk of multimorbidity associated with long sleep duration at older ages and in those with existing disease might reflect the need for longer sleep in those with underlying chronic conditions.

Automated summary

Sleep duration is associated with the incidence of chronic diseases and multimorbidity, but not with mortality. Long sleep duration at age 50 is not significantly associated with the risk of chronic disease.