Predictors of seven-year change in homocysteine concentrations in the Coronary Artery Risk Development in Young Adults (CARDIA) Study
While blood level of total homocysteine (tHcy) is inversely related to folate intake in cross-sectional studies, few prospective studies have examined changes in tHcy, folate intake, and cardiovascular disease (CVD) risk factors. Serum tHcy was measured on 755 18-30 year old participants in the Coronary Artery Risk Development in Young Adults (CARDIA) Study using stored samples from 1985-86 (baseline) and 1992-93 (Year 7), collected prior to food fortification with folic acid. Geometric mean tHcy did not differ by race at baseline (p>0.05). However by Year 7, mean tHcy was higher in blacks than whites (14.3, 13.3, 11.9, 10.9 μmol/L in black men, white men, black women, white women, respectively; p=0.001). Arithmetic mean change in tHcy differed from zero among blacks (1.3-1.4 μmol/L; p<0.001) but not among whites ( -0.3-0.2 μmol/L). Mean folate intake (from diet and supplements) at baseline was higher among whites than blacks within each sex (384, 439, 291, 349 μg, respectively; p=0.001). Although mean folate intake increased in all groups by Year 7, intake was higher among black than white men but the reverse was found among women (517, 496, 339, 421 μg; p for interaction=0.002). In multivariate models, change in tHcy was associated inversely with change in total folate intake in all race-sex groups; changes in smoking status among black men, in serum cholesterol level among whites, and in body mass index among white men were also independent predictors. Thus, tHcy increased over 7 years in blacks by 1.3-1.4 μmol/L (about 1 s.d.) on average, despite increases in folate intake. Changes in CVD risk factor status may help explain this contradictory finding.