Is sunlight exposure a risk factor for age-related macular degeneration? A systematic review and meta-analysis

Background Epidemiologists have recently investigated sunlight exposure as a risk factor for age-related macular degeneration (AMD), but there remains an ongoing dispute over this association due to insufficient evidence and unreliable data. Objectives To analyse comprehensively the epidemiological literature concerning the association between AMD and sunlight exposure. Methods We systematically reviewed the epidemiological literature concerning the association between AMD and sunlight exposure. An electronic search was performed of PubMed, Web of Science and CNKI, which was supplemented by hand searching. The selection of studies, data abstraction and quality assessment were performed independently by three reviewers. After these steps, we performed a random-effects meta-analysis, followed by subgroup analysis and sensitivity analysis, including a random-effects meta-regression for study-specific covariates. Results Fourteen studies were identified. Twelve studies identified an increasing risk of AMD with greater sunlight exposure, six of which reported significant risks. The pooled OR was 1.379 (95% CI 1.091 to 1.745). The subgroup of non-population-based studies revealed a significant risk (OR 2.018, 1.248 to 3.265, p=0.004). We identified the gross domestic product (GDP) per capita (p=0.048), but not the latitude (p=0.21), as a factor that led to heterogeneity according to the meta-regression. Conclusions The epidemiological literature published to date indicates that individuals with more sunlight exposure are at a significantly increased risk of AMD. The OR significantly decreased with increasing GDP per capita.