Difference in the homocysteine-lowering effect of folic acid in haemodialysis patients with and without occlusive vascular disease

Background. Hyperhomocysteinaemia has been identified as an independent cardiovascular risk factor and is found in more than 85% of patients on maintenance haemodialysis. Previous studies have shown that folic acid can lower circulating homocysteine in dialysis patients. We evaluated prospectively the effect of increasing the folic acid dosage from 1 to 6 mg per dialysis on plasma total homocysteine levels of haemodialysis patients with and without a history of occlusive vascular artery disease (OVD). Methods. Thirty-nine stable patients on high-flux dialysis were studied. Their mean age was 63 +/- 11 years and 17 (43%) had a history of OVD, either coronary and/or cerebral and/or peripheral occlusive disease. For several years prior to the study, the patients had received an oral post-dialysis multivitamin supplement including 1 mg of folic acid per dialysis. After baseline determinations, the folic acid dose was increased from 1 to 6 mg/dialysis for 3 months. Results. After 3 months, plasma homocysteine had decreased significantly by approximate to 23% from 31.1 +/- 12.7 to 24.5 +/- 9 mu mol/l (P = 0.0005), while folic acid concentrations had increased from 6.5 +/- 2.5 to 14.4 +/- 2.5 mug/l (P < 0.0001). However, the decrease of homocysteine was quite different in patients with and in those without OVD. In patients with OVD, homocysteine decreased only marginally by <approximate to>2.5% (from 29.0 +/- 10.3 to 28.3 +/- 8.4 mu mol/l, P = 0.74), whereas in patients without OVD there was a significant reduction of approximate to 34% (from 32.7 +/- 14.4 to 21.6 +/- 8.6 mu mol/l, P = 0.0008). Plasma homocysteine levels were reduced by >15% in three patients (18%) in the group with OVD compared with 19 (86%) in the group without OVD (P = 0.001), and by > 30% in none of the patients (0%) in the former group compared with 13 (59%) in the latter (P = 0.001). Conclusions. These results indicate that the homocysteine-lowering effect of folic acid administration appears to be less effective in haemodialysis patients having occlusive vascular disease than in those without evidence of such disease.