Plasma Homocysteine, Folate and Vitamin B12 Levels as Risk Factors for Coronary Artery Disease in a Turkish Cohort

Elevated levels of plasma homocysteine has emerged to be a new independent risk factor for coronary artery disease (CAD), but its importance in Turkish population is not well known. The present case-control study was designed to examine the relation between plasma homocysteine and CAD; and to establish whether the blood levels of folate and vitamin B12 that modulate plasma homocysteine levels relate to CAD. We compared 168 patients with CAD with 126 age- and sex-matched controls. Conventional risk factors and levels of plasma homocysteine, folate and vitamin B12 were documented. Concentrations of homocysteine levels were significantly higher in cases than in controls (geometric mean 12.6 [95% CI 12.4-12.8] vs 11.1 [10.8-11.3] pmol/L; p=0.001). Within the group of cases, there was a graded increase in the relative risk of CAD in the second, third, fourth and fifth quintiles of the homocysteine distribution (age adjusted odds ratios 1.43, 1.87, 2.15, 2.37; p=0.05) relative to the first quintile. In addition, the odds ratio for CAD in subjects with a homocysteine concentration above the 90th percentile of the control group, as compared with those whose homocysteine levels were at or below that value, was 2.35 (95% CI 1.21-4.74, p=0.009). On multivariate analysis when all other conventional risk factors were accounted for, plasma homocysteine levels remained an independent significant predictor of CAD (p=0.02). Mean folate levels were similar in both case and control subjects (8.1±3.5 vs 8.8±4.1 ng/ml; p=0.1). However, a level of foIate below the 10th percentile for control subjects conferred an odds ratio of 2.05 (95% CI 1.02-4.11, p=0.03) for CAD. Vitamin B12 levels were not different in cases (341 ± 137 pmol/L) and controls (357± 163 pmol/L) (p=0.3), and vitamin B12 deficiency ( <10th percentile for control subjects) was not associated with an increased odds ratio for CAD (1.19; [95% CI 0.51-2.80], p=0.6). Furthermore, plasma folate and vitamin B12 concentrations were inversely associated with homocysteine levels (r=-0.37, p<0.0001; r=-0.29, p=0.001, respectively). In conclusion, high plasma homocysteine levels are associated with an increased risk of CAD in Turkish population.