Sleep duration and mortality, influence of age, retirement, and occupational group

Summary Previous work has shown that both long and short sleep duration is associated with increased mortality, with lowest risk around 7 hr. This has had widespread impact on views on the optimal sleep duration. However, age, being employed/retired, and blue‐/white‐collar status, may influence the time available for sleep and thus, confound the association. We investigated the role of these factors on the association between sleep duration and mortality. We used employed and retired participants (N = 25,430) from the Swedish National March Cohort and Cox proportional hazards regression to model the shape of the association. We found a significant U‐shaped association in a multivariable model with a hazard ratio (HR) of 1.24 (95% confidence interval [CI] 1.10, 1.39) for 60.3 years at baseline. The shape of the association did not differ between blue‐/white‐collar workers, nor between employed and retired groups. We conclude that the U‐shaped association between sleep duration and mortality is present only in older individuals.