Background: The aim of this study was to find the prevalence of inherited and lifestyle-related risk factors for hypertension and their association with hypertension specified for age and sex.
Material and method: The study was based on data from 62,296 people aged 20-79 who participated in the second health study for Nord-Trøndelag county (HUNT2). The prevalence of hypertension was examined in people with measured blood pressure and body mass index (BMI) in addition to information on use of medication for hypertension, and hypertension in first degree relatives. In a subgroup not using medication for hypertension we used multiple linear regression to model the blood pressure as a function of lifestyle-related factors and information on cardiovascular disease and diabetes in first degree relatives.
Results: The prevalence of hypertension was examined in 42,117 subjects and varied from 7 % to 85 % for the different gender and age groups. Around 15 % were obese and approximately 50 % reported hypertension in relatives. Obesity as a single risk factor was associated with an up to four times higher risk of hypertension. In women aged 20-29 there was a synergistic interaction of hypertension in relatives and obesity, whereas the relationship was additive in the other sex and age categories. For 30,577 persons with complete data, blood pressure was modelled mathematically. In subjects with hypertension in relatives the systolic blood pressure was 3 mmHg higher for both genders. In obese subjects the systolic blood pressure was 10 and 7 mmHg higher than in corresponding reference groups of women and men respectively.
Interpretation: Hypertension in relatives and obesity are frequently occurring and strongly associated with hypertension. The relative risk of hypertension was particularly high in young obese women. In this group there was a statistically significant synergistic interaction between these risk factors for hypertension.