Abstract
Contrasting results have been reported regarding the associations between plasma total homocysteine (tHcy) and B vitamin levels and age-related macular degeneration (AMD) risk. Thus, we aimed to systematically evaluate these associations. Relevant case control studies in English were identified via a thorough search of the PubMed, Medline, and Embase databases from inception to June 2014. The results were pooled using Review Manager 5.2.1. Eleven studies (including 1072 cases and 1202 controls) were eligible for analysis of tHcy levels; additionally, 3 studies (including 152 cases and 98 controls) were eligible for analysis of folic acid and vitamin B12 levels. The cumulative results demonstrated that the plasma tHcy level among the AMD cases was 2.67 μmol/L (95% confidence interval [CI], 1.60-3.74) higher than that among the controls. In contrast, the vitamin B12 level among the AMD cases was 64.16 pg/mL (95% CI, 19.32-109.00) lower than that among the controls. Subgroup analyses showed that the folic acid level was 1.66 ng/mL (95% CI, 0.10-3.21) lower for the wet type. Together, the results demonstrated that AMD is associated with elevated tHcy levels and decreased vitamin B12 levels. Plasma tHcy may act as a modulator of the risk for AMD based on the current evidence.