The association of waist circumference with ambulatory blood pressure is independent of alternative adiposity indices

Abstract

The relationship between waist circumference (WC) and conventional blood pressure (BP) is independent of other clinical indices of adiposity. As ambulatory BP may offer more prognostic information than conventional BP, we aimed to identify whether indices of central adiposity are associated with ambulatory BP independent of other indices of adiposity. The relationship between indices of adiposity [WC, waist-to-hip ratio, body mass index (BMI) or skin-fold thickness] and ambulatory or conventional BP was determined in 300 randomly selected individuals of African descent living in an urban developing community in South Africa. Relationships were determined with multiple indices of adiposity in the same regression model and after adjusting for age, gender, alcohol and tobacco intake, the presence or absence of diabetes mellitus or inappropriate blood glucose control [haemoglobin A1c (HbA1c)], antihypertensive therapy and menopausal status. Sixty-five per cent of participants were overweight or obese. With respect to the relationships between indices of adiposity, BMI and WC showed the strongest correlation (r=0.84, P<0.0001). After including all indices of adiposity and confounders in the model, WC was the only clinical index of adiposity which independently predicted 24-h (partial r=0.15, P<0.005) and conventional (partial r=0.14, P<0.005) systolic BP and 24-h (partial r=0.13, P<0.02) and conventional (partial r=0.40, P<0.0001) diastolic BP. After adjusting for other adiposity indices and confounders, every 1 SD (15 cm) increase in WC resulted in a 4.04 mmHg increase in 24-h systolic BP and a 4.33 mmHg increase in 24-h diastolic BP. Similar results were obtained in the subgroup of 237 participants not receiving antihypertensive therapy. WC is the only clinical index of adiposity that is associated with 24-h and conventional BP independent of other adiposity indices in a community with a high prevalence of obesity.