The Associations Between Blood Levels of Homocysteine, Folate, Vitamin B12, and Retinal Vascular Caliber

PurposeTo assess the association of total serum levels of homocysteine (tHcy), folate, and vitamin B12 with retinal vascular caliber in older adults.DesignCross-sectional, population-based study.MethodsOne thousand seven hundred and seventy-two of 2334 Blue Mountains Eye Study participants examined had fundus photographs taken and retinal arteriolar and venular caliber measured using computer-assisted techniques and summarized. Serum folate and vitamin B12 levels and tHcy were determined from venous blood samples. Linear regression models adjusting for age, gender, mean arterial blood pressure, smoking, and diabetes were used to assess whether serum levels of tHcy, folate, and vitamin B12 were associated with retinal arteriolar and venular caliber.ResultsArteriolar and venular caliber was not associated with tHcy in the total population. Further analysis demonstrated a significant serum homocysteine–gender interaction (P = .04). A significant inverse association between tHcy and arteriolar caliber was found in men only (P = .03), with a threshold detected at a level of 17 μmol/l. Above this threshold, increasing tHcy was linearly associated with narrower arteriolar caliber (0.86 μm reduction per 1.0 μmol/l increase in tHcy) in men, but no significant association was found below this threshold. No significant associations were observed between serum folate or vitamin B12 levels and either retinal vessel caliber.ConclusionsRetinal vascular caliber is associated with tHcy in men but not women. This finding may reflect the stronger association between blood pressure and tHcy in men than in women.