Does High Altitude Increase the Risk of Retinal Vein Occlusion due to Elevated Serum Homocysteine?

To determine if prolonged high-altitude exposure and resulting hyper-homocysteinemia are the independent risk factors for retinal vein occlusion.

Serum levels of homocysteine, Vitamin B12, and folate were quantified using competitive immunoassay with electrochemiluminescence in patients newly diagnosed with retinal vein occlusion residing in the lesser Himalayas. Age-matched controls without venous occlusions were chosen from the same population. Patients living at altitudes below 2000 m above sea level were excluded from the study. The sensitivity and specificity of serum homocysteine in predicting venous occlusion were determined using receiver operating characteristic (ROC) curve analysis. Multivariate logistic regression was performed to identify independent risk factors for retinal vein occlusion, after adjusting for known confounders such as gender, diabetes, hypertension, glaucoma, hyperlipidemia, and smoking.

This study of 200 subjects, divided into cases and controls, found that hyperhomocysteinemia prevalence was 78% among the cases and 47% among the controls. The mean serum homocysteine levels in individuals living at elevations above 3800 m (29.1 ± 10 μM/L) were significantly higher (P < 0.001) compared to those residing at elevations below 3800 m (15.8 ± 8 μM/L). The cut-off value of serum homocysteine, determined by coordinate points on the ROC curve, was 18.8 μM/L. Logistic regression found strong links between retinal vein occlusion and high homocysteine (odds ratio [OR] = 2.62) and living above 3800 m (OR = 1.42).

Prolonged exposure to high altitude results in elevated homocysteine levels, indicating a potential association between hyperhomocysteinemia and retinal vein occlusion.