MALONDIALDEHYDE LEVELS IN PATIENTS WITH AGE-RELATED MACULAR DEGENERATION: A Systematic Review and Meta-analysis.

BACKGROUND/PURPOSE: The role of blood malondialdehyde (MDA) in age-related macular degeneration (AMD), the leading cause of new blindness in industrialized countries, is still matter of debate. We performed a systematic review and meta-analysis of the published data on the MDA levels in AMD patients. METHODS: PubMed, ISI Web of Sciences, and Scopus searches were performed according to MOOSE guidelines. Case-control studies were eligible for inclusion. Participants and controls were AMD patients and subjects without AMD, respectively. The main outcome measures were wet AMD and dry AMD. MDA level was the main exposure variable. Data were pooled using a random-effects model. RESULTS: Twelve case-control studies were identified. A total of 634 AMD patients (mean age 66.7 years) and 656 controls without AMD (mean age 67.8 years) were evaluated. Extreme between-study heterogeneity was observed (I = 96.8%, P < 0.001). Pooled standardized mean difference showed that MDA values were significantly higher in patients with AMD (standardized mean difference = 1.91 µmol/L, 95% confidence interval = 1.08-2.74; P < 0.001). In a model including five studies, homogenous for age, sample matrix, and laboratory testing for MDA, heterogeneity decreased from extreme to moderate (I = 46.4%, P = 0.113), and pooled standardized mean difference, though attenuated, remained significantly higher in AMD patients (standardized mean difference = 1.07 µmol/L, 95% confidence interval = 0.82-1.31; P < 0.001). CONCLUSION: There is some evidence of higher levels of MDA in AMD patients compared with healthy controls; however, this result should be interpreted with caution because of extreme between-study heterogeneity and the possible effect of publication bias. Future studies, preferably well age-matched and of cohort design, are necessary before any firm conclusions on the putative role of elevated MDA on AMD can be drawn.