Impact of waist circumference on the relationship between blood pressure and insulin -: The Quebec Health Survey

Hyperinsulinemia has been suggested to be involved in the etiology of obesity- associated hypertension. The objective of the present study was to quantify, in a population- based study, the respective contributions of excess adiposity ( body mass index [ BMI]), waist circumference ( WC), fasting insulin levels, and insulin sensitivity to the variation of resting blood pressure. The Quebec Health Survey was used to obtain fasting plasma insulin and glucose levels and resting blood pressure as well as anthropometric measurements in a representative sample of 907 men and 937 women. When the sample was divided into tertiles of BMI and further stratified on the basis of the 50th percentile of WC ( 88 cm in men), nonobese men in the first BMI tertile ( < 23.2 kg/ m(2)) but with abdominal obesity were characterized by an increased systolic blood pressure ( SBP) compared with nonobese men with low WC ( 130 +/- 18 versus 120 +/- 11 mm Hg; mean +/- SD; P = 0.075). The SBP was comparable to SBP values measured among men in the top BMI tertile ( 129 +/- 14 mm Hg for BMI >= 26.6 kg/m(2)). When subjects were classified into tertiles of fasting insulin and WC, no association between insulin levels and blood pressure was noted, once the variation in WC was considered. Insulin sensitivity ( estimated with homeostasis model assessment [ HOMA]) did not explain variation in blood pressure in men, whereas the contribution of HOMA in women was of marginal clinical significance ( R-2 of < 1.3%; P < 0.0001). These results suggest that the documented association between obesity, fasting insulin, insulin sensitivity, and blood pressure is largely explained by concomitant variation in WC.