The association between visual impairment and the risk of mortality: a meta-analysis of prospective studies

Background The findings from prospective studies on visual impairment (VI) and the risk of mortality are not consistent. Objective A meta-analysis of prospective studies was conducted to quantitatively summarise the evidence about the association between VI and the risk of mortality. Methods Pertinent studies were identified by a search of PubMed, Web of Science and the Chinese National Knowledge Infrastructure and Wanfang databases up to December 2015. The random-effect model was used to combine study-specific relative risks (RRs) and 95% CIs. Meta-regression and subgroup analysis were conducted to explore potential sources of heterogeneity. Publication bias was estimated by Egger's test and the funnel plot. Dose-response relationship was assessed by restricted cubic spline functions. Results This meta-analysis contained 29 prospective studies including 269 839 participants and 67 061 deaths. Compared to the no VI, the highest VI level was significantly associated with an increased risk of mortality (RR: 1.36, 95% CI 1.25 to 1.46). The association remained significant in participants older than 65 years (RR: 1.28, 95% CI 1.18 to 1.39), and a significant association was also observed in men (RR: 1.29, 95% CI 1.07 to 1.54) and women (RR: 1.39, 95% CI 1.14 to 1.70), respectively. For dose-response analysis, a linear relation was found between visual acuity (VA) and the risk of mortality. For every 0.1 Logarithm of the Minimum Angle of Resolution (LogMAR) increment, the risk of mortality increased by 4% (RR: 1.04, 95% CI 1.01 to 1.06). Conclusions VI was significantly associated with an increased risk of mortality.