Aims/hypothesis: This study aimed to investigate whether the effects of sleep duration interacted with the presence of diabetes. We specifically sought to examine the relationship between sleep duration and all-cause and cause-specific mortality in people with type 2 diabetes across sex, age at diagnosis, duration of diabetes and treatment type.
Methods: The sample consisted of 273,029 adults, including 248,817 without diabetes and 24,212 with type 2 diabetes, who participated in the National Health Interview Survey from 2004 to 2013 and whose data were linked to a mortality database up to 31 December 2015. Sleep duration was measured using self-report, whereby participants were asked 'on average how long do you sleep each day (≤5, 6, 7, 8, 9 or ≥10 h/day)?' The relationship between sleep duration and mortality risk was investigated using Cox proportional hazards regression model, with adjustments for demographics, BMI, lifestyle behaviours and clinical variables.
Results: Absolute mortality rate was higher in adults with diabetes and extremes of sleep duration (≤5 h/day, 215.0 per 10,000 person-years; ≥10 h/day, 363.5 per 10,000 person-years). There was a non-significant interaction between sleep duration and the presence of diabetes (p for interaction = 0.08). A J-shaped relationship existed between sleep duration and all-cause mortality risk in people with type 2 diabetes. Compared with the reference group (7 h/day), both shorter and longer sleep durations were associated with increased risk of all-cause mortality (≤5 h/day, HR 1.24 [95% CI 1.09, 1.40]; 6 h/day, HR 1.13 [1.01, 1.28]; 8 h/day, HR 1.17 [1.06, 1.30]; ≥10 h/day, HR 1.83 [1.61, 2.08]). Similar associations were also observed for mortality risk from CVD, cancer, kidney disease, Alzheimer's disease and chronic lower respiratory diseases. Longer sleep duration in those with a younger age at diabetes onset was associated with greater risks of all-cause and CVD mortality. Shorter sleep duration in individuals treated with both insulin and oral glucose-lowering medication was also associated with higher risks of all-cause and CVD mortality.
Conclusions/interpretation: The associations between sleep duration and mortality risk may be different between diabetic and non-diabetic individuals. In people with type 2 diabetes, sleeping less or more than 7 h/day was associated with increased risk of all-cause and condition-specific mortality. The association was more prominent in those with a younger age at diabetes onset and receiving treatment with both oral glucose-lowering medication and insulin. This population may benefit from targeted sleep-related interventions to reduce the risks of adverse health outcomes. Graphical abstract.
Keywords: Cohort study; Diabetes mellitus; Mortality; Sleep duration.