1. Body composition measures as predictors of hypertension in urban black South African woman

Abstract

Objectives: Hypertension is becoming increasingly prevalent in South Africa (SA), especially amongst the black population. Since body composition is a major risk factor for hypertension, it is important to investigate which parameter of body composition best predicts this disease. The aim of this study was to evaluate whether baseline and/or change in body composition, could predict the development of hypertension over a 10 year period in a sample of black SA woman. Research design and methods: This longitudinal study included 563 black SA women, aged 29-53 years, residing in Soweto, Johannesburg. Data on systolic and diastolic blood pressure, anthropometric, dual energy x-ray absorptiometry (DXA)-derived body composition and simple anthropometric measures were collected at baseline (2003) and at 10-year follow-up (2013). Results: Over the 10-year follow-up period, all anthropometric [eg. body mass index (BMI): 30.3±6.1 to 32.6±6.8, p<0.0001], DXA-derived body composition measures (p<0.001) and blood pressure (BP, systolic: 19.8±19.8 mmHg, diastolic: 12.6±12.0 mmHg; both p<0.001) increased significantly. A total of 321 participants (cumulative incidence 57.02%) developed hypertension [systolic (and/or diastolic) BP >140 (90) mmHg) during follow-up. Baseline BMI and waist circumference were associated with the development of hypertension at follow-up [adjusted odds ratio (95% CI) per unit change: 1.04 (1.01-1.08), p=0.012 and 1.03 (1.01-1.04), p=0.001, respectively]. Of the DXA-derived measures of body composition and body fat distribution, fat mass [adjusted odd ratio (95% CI) per unit change: 1.03 (1.00-1.05), p=0.049], fat mass (%) (1.05 (1.01-1.09), p=0.008), trunk fat mass (1.05 (1.00-1.11), p=0.046), arm fat mass (% total fat mass) (1.19 (1.04-1.37), p=0.013) and leg fat mass (% total fat mass) (0.96 (0.92-0.99), p=0.025) at baseline were also associated with increased risk for hypertension risk at follow-up. The changes in anthropometric and DXA-derived measures of body composition were not associated with hypertension at follow- up. Conclusion: Our study has shown that baseline body composition, rather than the change in body composition, is the better predictor of future risk of developing hypertension.