INTRODUCTION
The causes of high blood pressure are complex and based on an interaction between multiple biological factors and behaviours. Insulin resistance and inflammation are commonly acknowledged mechanisms in the development of CVD, while insulin resistance and relative body weight correspondingly predict the development of high blood pressure.
HYPOTHESIS
We aimed to compare insulin resistance, relative body weight, and inflammation in the association with SBP.
METHODS
In 2001-2005 a random sample of residents aged 30-74 years in the municipalities of Vara and Skövde, South-western Sweden, were invited to a survey of cardiovascular risk factors. In all 1811 participants in Vara (participation rate 81%) and 1005 participants in Skövde (70%) were enrolled. Subjects with a known history of hypertension were excluded for the current study. Specially trained nurses saw all subjects in the morning after a 10 hours over night fast, and venous blood samples were taken. A physical examination included body height and body weight (light cloths and no shoes), blood pressure was measured twice in a supine position after a 5 minutes rest (arm in heart level). The mean of the 2 measurements was used for statistical analyses. Hs-CRP and plasma insulin were analysed, and BMI and HOMA-index were calculated using standard algorithms. The log form of HOMA-ir was used in statistical analyses. Associations were explored in males and females separately using multivariate linear regression.
RESULTS
In all 2538 subjects, 1266 men (50%) and 1272 women (50%) without known hypertension were included. BMI and HOMA-ir were both significantly associated with SBP in both males and females, while hs-CRP was associated with SBP in women only. These factors were accordingly entered into a multivariate linear regression model also including age. In men HOMA-ir [regression coefficient, (95% confidence interval), and p-value] [5.4 (2.5-8.4), p<0.001], was significantly associated with SBP, while BMI [0.2 (-0.3-0.5), p=0.087], and CRP was not [0.02 (-0.1-0.1), p=0.138]. In women all three mechanisms came out significantly; HOMA-ir [5.4 (2.2-8.6), p<0.001], BMI [0.4 (0.2-0.5), p<0.001], and CRP [0.2 (0.02-0.4), p=0.031]. There were statistically significant interaction terms between gender and CRP (p=0.037), and gender and HOMA-ir (P=0.045), respectively, while no corresponding interaction was found for BMI. CONCLUSIONS Our study confirms a strong impact of insulin resistance and relative body weight on blood pressure levels in both men and women. However, a significant association between hs-CRP and systolic blood pressure in women was not seen in men. Gender differences in insulin resistance and inflammation were statistically confirmed by interaction terms. These findings have implications for future research and for development of clinical practice.
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