Low vitamin B6 and folic acid levels are associated with retinal vein occlusion independently of homocysteine levels

Retinal vein occlusion (RVO) is one of the most common retinal vascular disorders. During the last years, high levels of homocysteine (Hcy) have been demonstrated to be an independent risk factor for RVO. Aim of this study was to investigate the association among circulating B-group vitamins, Hcy and RVO. Thus, we studied 262 RVO patients and 262 age- and sex-comparable healthy subjects. Serum vitamin B6 was measured by HPLC, serum folic acid and vitamin B12 by radioimmunoassay and plasma Hcy by FPIA. Blood levels of vitamin B6, folate and Hcy, but not of vitamin B12, were found to be significantly different in patients as compared to healthy subjects. At the univariate analysis, the lowest tertile of vitamin B6 [odds ratio (OR) 4.03; 95% confidence interval (CI) 2.58–6.31; P < 0.0001)] and folate (OR 6.13; 95% CI 3.85–9.76, P < 0.0001), and the highest tertile of Hcy (OR 8.08; 95% CI 5.05–12.92, P < 0.0001) were found to be significantly associated with RVO. Moreover, at multivariate analysis, after adjustment for traditional cardiovascular risk factors, Hcy, and circulating levels of vitamins, respectively, the lowest tertile of vitamin B6 (OR 3.29; 95% CI 1.89–5.70, P < 0.0001) and folate (OR 5.41; 95% CI 3.08–9.51, P < 0.0001) and the highest tertile of Hcy (OR 2.58; 95% CI 1.12–5.94, P < 0.0001) maintained their significant association with RVO. In conclusion, the present study documents, on a large sample of patients, that low vitamin B6 levels, low folic acid levels and elevated Hcy levels are each independently associated with RVO.