Sex differences in the association between marital status and the risk of cardiovascular, cancer, and all-cause mortality: a systematic review and meta-analysis of 7,881,040 individuals

Purpose To ascertain whether sex differences exist in the relationship between marital status and cardiovascular diseases (CVD), coronary heart disease (CHD), cancer and all-cause mortality in the general population and to explore the potential effect of age, location, the duration of follow-up and publication years on these outcomes. Methods A systematic search was performed in PubMed and EMBASE from inception through to April 2018 and review of references to obtain sex-specific relative risks and their 95% confidence intervals. These were used to derive the women-to-men ratio of RRs (RRR) and 95% CI for each study. RRs and RRRs for each outcome were then pooled using random effects inverse-variance weighted meta-analysis. Results Twenty-one studies with 7,891,623 individuals and 1,888,752 deaths were included in the meta-analysis. Compared with married individuals, being unmarried was significantly associated with all-cause, cancer, CVD and coronary heart disease mortalities for both sexes. However, the association with CVD and all-cause mortality was stronger in men. Being divorced/separated was associated with a higher risk of all-cause mortality in men and a stronger risk of cancer and CVD mortality. The pooled ratio for women versus men showed 31 and 9% greater risk of stroke mortality and all-cause mortality associated with never married in men than in women. Conclusions Being unmarried conferred higher risk of stroke and all-cause mortality for men than women. Moreover, divorced/separated men had higher risk of cancer mortality and CVD mortality. Further studies are warranted to clarify the biological, behavioral, and/or social mechanisms involved in sex differences by these associations.