The genotype distribution among the 5,531 individuals was in Hardy-Weinberg equilibrium. Demographic data of the different genotype groups are shown in Table 1. No significant difference in gender, age, education level, body mass index, cholesterol level, smoking status, level of physical activity, diabetes-, stroke- or headache prevalence was found between the genotype groups. However, individuals with Val/Val genotype had lower prevalence of myocardial infarction (2.3% versus 3.6%, p < 0.05) and ischemic heart disease (myocardial infarction and/or angina pectoris) (5.7% versus 7.7%, p = 0.02) compared to those with the other genotypes (Table 1). The individuals with known genotype were significantly older and had, consequently, higher blood pressure and cholesterol level, higher prevalence of ischemic heart disease and chronic musculoskeletal pain, and had lower physical activity level than those with unknown COMT genotype (Table 1).
