Sleep and 24-hour activity rhythms and the risk of stroke: a prospective cohort study.

Introduction Short and long self-reported sleep durations are associated with a higher risk of stroke, but the association of objective estimates of sleep and 24-hour activity rhythms is less clear. We studied the association of actigraphy-estimated sleep and 24-hour activity rhythms with the risk of stroke in a population-based cohort of middle-aged and elderly. Methods We included 1718 stroke-free participants (mean age 62.2 ± 9.3 years, 55.1% women) from the prospective, population-based Rotterdam Study. Actigraphy-estimated sleep (total sleep time, sleep efficiency, sleep onset latency and wake after sleep onset) and 24-hour activity rhythms (interdaily stability, intradaily variability and onset of the least active 5 hours) were measured during a median of 7 days (Q1-Q3: 6-7 days). The association of sleep and 24-hour activity rhythms with risk of stroke was analyzed using Cox proportional hazards models. Results During a mean follow-up of 12.2 years (SD: 3.2), 105 participants developed a stroke, of whom 81 had an ischemic event. Although there was no clear association between actigraphy-estimated sleep and the risk of stroke, a more fragmented 24-hour activity rhythm was associated with a higher risk of stroke (hazard ratio [HR] per SD increase 1.28, 95% confidence interval [CI] 1.07-1.53). A less stable (HR per SD increase in stability 0.78, 95%CI 0.63-0.97) and more fragmented (HR 1.28, 95%CI 1.04 - 1.58) 24-hour activity rhythm were also associated with a higher risk of ischemic stroke. Conclusions Disturbed 24-hour activity rhythms, but not sleep, are associated with a higher risk of stroke in middle-aged and elderly persons. This suggests that unstable and fragmented activity rhythms may play a more prominent role in the risk of stroke than sleep per se.