The association between insomnia symptoms and risk of cardio-cerebral vascular events: A meta-analysis of prospective cohort studies

Background Insomnia symptoms have been suggested to be associated with the risk of cardio-cerebral events. However, the results of previous studies have been inconsistent. Therefore, we conducted a meta-analysis to examine whether there were associations between cardio-cerebral vascular events and insomnia symptoms, including difficulty initiating sleep, difficulty maintaining sleep, early-morning awakening or non-restorative sleep. Design A meta-analysis of prospective cohort studies. Methods PubMed, Web of science and the Cochrane Library were searched without language restriction. Prospective cohort studies of adults with at least a 2-year follow-up duration were included. Random effect models were used in order to pool the results for each insomnia symptom. Subgroup and sensitivity analyses were conducted in order to assess potential heterogeneity, and funnel plots and Egger's tests were used in order to assess publication bias. Results Fifteen studies (23 cohorts) were included. Positive associations were observed between difficulty initiating sleep, difficulty maintaining sleep and non-restorative sleep with risk of cardio-cerebral vascular events. The pooled relative risks and 95% confidence intervals were 1.27 (1.15-1.40), 1.11 (1.04-1.19) and 1.18 (1.05-1.33), respectively. However, less evidence existed to support the conclusions about the association between early-morning awakening and cardio-cerebral vascular events. Conclusion Our meta-analysis demonstrated that insomnia symptoms of difficulty initiating sleep, difficulty maintaining sleep and non-restorative sleep were associated with an increased risk of future cardio-cerebral vascular events.