The relationship of waist circumference to blood pressure: the Olivetti Heart Study

BACKGROUND: The association between overweight, high blood pressure (BP), and insulin resistance is well established, but the role of body fat distribution in this association has yet to be fully elucidated. The aim of this study was to investigate the role of central adiposity in the association between overweight, high BP, and insulin resistance. METHODS: A total of 1,079 men participated in the follow-up of the Olivetti Heart Study from 1994 to 1995. The present analysis includes 768 men, after the exclusion of 184 participants on pharmacological treatment for hypertension. In 65 men fasting blood glucose was >7 mmol/L; in 48, age was below or above 2 standard deviations from the mean of the population; and in 14 the data set was incomplete. Anthropometric indices of adiposity, metabolic variables (including fasting serum insulin and homeostasis model assessment [HOMA] index of insulin sensitivity), and BP were measured. RESULTS: In univariate analysis, waist circumference was the anthropometric index that best correlated with BP (P < .001). In multiple regression analysis, waist circumference remained the strongest independent predictor of BP after adjustment for confounders. Significant increase of systolic (P value for trend analysis < .001) and diastolic (P < .001) pressure, heart rate (P = .003), fasting and postload serum insulin (P < .001), and HOMA index of insulin sensitivity (P < .001) were observed across age-adjusted quintiles of waist circumference. Greater degrees of central adiposity were associated with higher prevalence of elevated BP values and insulin resistance (P value < .001, chi2 for linear trend). CONCLUSIONS: In middle-aged men, a central distribution of body fat is associated with increased BP, independently of body mass index and insulin resistance, thus suggesting a key role of central adiposity in the full expression of the "metabolic syndrome."