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B. Gopinath, J. J. Wang, G. Burlutsky, V. M. Flood, T. Y. Wong, P. Mitchell, Blue Mountains Eye Study; The Associations Between Retinal Vascular Caliber and Homocysteine, Folate and Vitamin B12 Levels. Invest. Ophthalmol. Vis. Sci. 2009;50(13):104.
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Investigators of the Hoorn Study observed a significant association between high total plasma homocysteine levels and retinal arteriolar narrowing. We aimed to assess the association between serum homocysteine, serum folate and vitamin B12 levels with retinal vascular caliber in the Blue Mountains Eye Study (BMES) population.
Of 2,335 BMES participants re-examined in 1997-9, 1,772 had retinal photographs taken to measure retinal arteriolar and venular caliber. Serum homocysteine, folate and vitamin B12 levels were determined using venous blood samples. Multivariable adjusted linear regression models were used to assess continuous associations with retinal vessel caliber and non-linear models were used to assess threshold effects on associations of homocysteine levels with retinal vascular caliber.
After adjusting for age, sex, fasting blood glucose, smoking and mean arterial blood pressure, persons with homocysteine level >20 µmol/L (clinical cut off) had significantly narrower mean retinal arteriolar diameter (189.3 µm) than those with homocysteine lower than this level (193.6 µm, p=0.01). However, in linear regression models, this association was not statistically significant (p=0.15). Further investigation showed a significant gender interaction (p=0.04), with associations seen only in men. Among men, a threshold effect was detected at a serum homocysteine level of 14 µmol/L, above which, increasing homocysteine level was associated with narrower arteriolar diameter (narrowing of 0.586 µm per 1.0 µmol/L increase in homocysteine levels), but below this threshold, no significant association was found. We found no associations of serum folate or B12 levels with retinal arteriolar or venular caliber.
We detected a significant association between elevated serum homocysteine level and retinal arteriolar caliber narrowing in men, with a threshold at 14 µmol/L. A possible mechanism could be that elevated homocysteine is more frequent in men, and may affect the retinal microvasculature by its effects on oxidative and inflammatory processes and endothelial cell dysfunction.
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