Prospective study of plasma homocysteine, its dietary determinants, and risk of age-related macular degeneration in men

Purpose: Cross-sectional and case-control studies generally support a direct association between elevated plasma homocysteine and age-related macular degeneration (AMD), but data from prospective studies are limited. We examined the prospective relation of plasma homocysteine level, its dietary determinants, and risk of AMD in a large cohort of apparently healthy male physicians. Methods: During a mean follow-up of 11.2 years, we identified 146 incident cases of visually significant AMD (responsible for a reduction of visual acuity to 20/30 or worse), and 146 controls matched for age, smoking status, and time of blood draw. We measured concentration of homocysteine in blood samples collected at baseline using an enzymatic assay. and we assessed dietary intake of B vitamins and related compounds betaine and choline with a food frequency questionnaire administered at baseline. Results: AMD was not associated with plasma level of homocysteine; the multivariable-adjusted odds ratio (OR) of AMD comparing the highest and lowest quartile of homocysteine was 1.09 (95% confidence interval [95% CI]: 0.52-2.31; p for trend = 0.99). However, AMD was inversely associated with quartile of intake of total folate (OR: 0.55; 95% CI: 0.24-1.23; p for trend = 0.08), vitamin B-6 from food (OR: 0.39; 95% CI: 0.17-0.88; p for trend = 0.01), and betaine (OR: 0.53; 95% CI: 0.22-1.27; p for trend = 0.048). Conclusions: These prospective data from a cohort of apparently healthy men do not support a major role for homocysteine in AMD occurrence, but do suggest a possible beneficial role for higher intake of several nutrients involved in homocysteine metabolism.