Sleep duration and risk of stroke: a dose-response meta-analysis of prospective cohort studies

Objectives: Suboptimal sleep duration has been considered to increase the risk of stroke incidence. Thus we aimed to conduct a dose-response meta-analysis to examine the association between sleep duration and stroke incidence. Methods: We searched PubMed, Web of science and the Cochrane Library to identify all prospective studies evaluating the association of sleep duration and nonfatal and/or fatal stroke incidence. Then, restricted cubic spline functions and piecewise linear functions were used to evaluate the nonlinear and linear dose-response association between them. Results: We included a total of 16 prospective studies enrolling 528,653 participants with 12,193 stroke events. Nonlinear dose-response meta-analysis showed a J-shaped association between sleep duration and total stroke with the lowest risk observed with sleeping for 7 h. Considering people sleeping for 7 h as reference, long sleepers had a higher predicted risk of total stroke than short sleepers [the pooled risk ratios (95% confidence intervals): 4 h: 1.17 (0.99-1.38); 5 h: 1.17 (1.00-1.37); 6 h: 1.10 (1.00-1.21); 8 h: 1.17 (1.07-1.28); 9 h: 1.45 (1.23-1.70); 10 h: 1.64 (1.4-1.92); P-nonlineanty<0.001]. Short sleep durations were only significantly associated with nonfatal stroke and with total stroke in the subgroups of structured interview and non-Asian countries. Additionally, we found a slightly decreased risk of ischemic stroke among short sleepers. For piecewise linear trends, compared to 7 h, every 1-h increment of sleep duration led to an increase of 13% [the pooled risk ratios (95% confidence intervals): 1.13 (1.07-1.20); p < 0.001] in risk of total stroke. Conclusion: Both in nonlinear and piecewise linear dose response meta-analyses, long sleep duration significantly increased the risk of stroke incidence. (C) 2016 Elsevier B.V. All rights reserved.