Purpose: We conducted a meta-analysis to evaluate the relationship between smoking and age-related cataract (ARC).
Methods: Eligible studies were identified via computer searches and reviewing the reference lists of the key articles. The summary relative risk ratio (RR) or odds ratio (OR) and 95% confidence interval (CI) were calculated. Study-specific risk estimates were pooled using a random-effects model. Meta-regression to assess heterogeneity by several covariates and subgroup analysis on ARC types were performed.
Results: A total of 13 prospective cohort and eight case-control studies met our inclusion criteria. Ever smoking was statistically significantly associated with increased risk of ARC among cohort studies (OR 1.41, 95% CI 1.23-1.62) and case-control studies (OR 1.57, 95% CI 1.20-2.07). In subgroup analysis, ever smoking exhibited a positive relationship with nuclear cataract (NC; OR 1.66, 95% CI 1.46-1.89) and a marginally significant relationship with posterior subcapsular cataract (OR 1.43, 95% CI 0.99-2.07) in cohort studies. Similar results were found in case-control studies (NC OR 1.86, 95% CI 1.47-2.36; posterior subcapsular cataract OR 1.60, 95% CI 0.97-2.65). Current smokers were at higher risk of ARC than past smokers. No association between smoking and cortical cataract was observed.
Conclusions: The overall current literature suggests that smoking was associated with increased risk of ARC, especially NC. Further efforts should be made to confirm these findings and clarify the underlying biological mechanisms.