Regional serum cholesterol differences in Belgium: do genetically determined cardiovascular risk factors contribute?

Background Differences in serum lipid distribution and mortality from ischaemic heart disease have repeatedly been reported between Belgian northerners and southerners. We investigated whether serum lipoprotein(a) (Lp(a)) and apolipoprotein (apo) E polymorphism were involved. Methods Fasting serum lipids, apo A-I and B, and Lp(a) levels were examined in randomly selected, 20-39 year old Belgian males and females from the north (Flanders) and the south (Wallonia) of Belgium (N = 900). Apo E phenotype distribution was investigated in random subsamples from either region (N = 249). Results Mean serum cholesterol, low density lipoprotein cholesterol (LDL-c), apo B and triglyceride levels were higher in Walloons compared to Flemings within each gender, the difference being significant in 30-39 year old males. Average high density lipoprotein cholesterol and apo A-I levels were significantly lower in 30-39 year old male southerners, compared to their northern counterparts. Median Lp(a) was 67 mg/l in northerners and 75 mg/l in southerners (NS). The apo E phenotype distribution was similar in both regions (chi(2) = 7.213; d.f. = 5; P = 0.2053), whereas the average effects of the apo E alleles differed between the regions. In southerners the epsilon 4 effect upon adjusted apo B and LDL-c levels was approximate to+12% and the epsilon 2 effect was approximate to-15%; in northerners the epsilon 4 and epsilon 2 effects were approximate to+5% and approximate to-25%, respectively The apo E polymorphism did not affect serum Lp(a) levels. Conclusions Regional cholesterol differences between Flemings and Walloons cannot be explained by differences in serum Lp(a) or apo E phenotype distribution. The less favourable epsilon 2 and epsilon 4 effects in southerners compared to northerners reflect modulation of the apo E gene by particular environments.