Relationship between homocysteine level and diabetic retinopathy: a systematic review and meta-analysis

Background: The relationship between homocysteine (Hcy) and diabetic retinopathy (DR) remains unclear to date. Therefore, a systematic review and meta-analysis was performed on the relationship between Hcy level and DR. Methods: Studies were identified by searching PubMed, Embase, and Web of Science databases until 5 May, 2014. Results: A total of 31 studies involving 6,394 participants were included in the meta-analysis. After pooling the data from each included study, the blood Hcy concentration in the DR group was observed to be higher than that in the control group [WMD = 2.55; 95% confidence interval (CI), 1.70-3.40], and diabetes mellitus (DM) patients with hyperhomocysteinemia were at a risk for DR [odds ratio (OR) = 1.93; 95% CI, 1.46-2.53]. Considering the different DM types, hyperhomocysteinemia in T1DM (OR = 1.83, 95% CI, 1.28-2.62) was associated with DR rather than in T2DM (OR = 1.59, 95% CI, 0.72-3.51). Considerable statistical heterogeneity in the overall summary estimates was partly explained by the geographical differences. Conclusions: Results from this current meta-analysis indicate that hyperhomocysteinemia is a risk factor for DR, especially proliferative DR. Differences between geographical regions were observed in the relationship between hyperhomocysteinemia with T1DM risk. Given the heterogeneous results, the relationship between high Hcy and DR needs further investigation.