Insomnia subtypes and the subsequent risks of stroke: report from a nationally representative cohort.

BACKGROUND AND PURPOSE The studies assessing the impact of insomnia on stroke are still lacking. We aim to investigate insomnia in relation to subsequent stroke during the 4-year follow-up. METHODS Data from the Taiwan National Health Insurance Research Database were used. Enrollees with International Classification of Diseases, Ninth Revision, Clinical Modification diagnosis code for insomnia were compared with randomly selected, age- and sex-matched noninsomnia enrollees with subsequent hospitalization for stroke during the 4-year follow-up. All enrollees, insomniacs and noninsomniacs, did not have previous diagnosis of stroke, sleep apnea, and insomnia. Individuals with insomnia were further categorized into different subgroups based on their insomnia patterns to explore whether the risk of stroke varies by subtype. The risk of outcomes was assessed with Kaplan-Meier curves and the impact of insomnia was estimated using Poisson regression analysis and Cox proportional hazards models. RESULTS The study included 21,438 (mean age, 52±16 years) insomniacs and 64,314 matched noninsomniacs (mean age, 51±16 years). Compared with noninsomniacs, insomniacs had 54% higher risk of developing stroke (adjusted hazard ratio, 1.54; 95% confidence interval, 1.38-1.72). When breaking down into insomnia subgroups, the persistent insomniacs had a higher 3-year cumulative incidence rate of stroke than those in the remission group (P=0.024). The insomniacs-to-noninsomniacs incidence rate ratio for stroke was highest among those aged 18 to 34 years (incidence rate ratio, 8.06). CONCLUSIONS Insomnia predisposes individuals to increased risk of stroke and this association is profound among young adults. Our results underscore the clinical importance of identifying and treating insomnia. A novel behavioral intervention targeting insomnia that may prevent stroke should be explored.