The variables height, weight, BMI, age, and genotype showed an association with blood pressure (P < 0.05); therefore, they were included in a stepwise logistic regression to study the possible combined effect of mutant C602A and T1559C alleles and other risk factors on hypertension. The remaining variables that were closely associated with BP were BMI, C602A, T1559C, height and weight after adjusting for age and sex (Table 4). In the haplotype-based case-control analysis, haplotypes were established in three representative common SNPs (Table 5). An association with hypertension was found in the linkage disequilibrium (LD) block (r2 > 0.5, D' > 0.9). C602A and T1559C in the block were significantly associated with hypertension (P = 0.033 and P = 0.007, respectively; Figure 1).