Associations between adiposity and hypertension using a simple proxy for adiposity and a direct measure of fatness in adolescent and adult Namibians

Abstract

Obesity rates are increasing among adolescents across sub-Saharan Africa, which are related to increasing hypertension. Obesity, as defined by body mass index (BMI) equal to or greater than thirty kilograms per meter squared (BMI of ≥30 kg/m²), is well established as a risk factor for hypertension in adolescence and adulthood. However, BMI is a crude proxy for body fatness and/or obesity, particularly among African populations. This study sought to compare the associations between hypertension and adiposity as measured by BMI vs adiposity as assessed by deuterium dilution method (DDM) in Namibian adolescent and adult females. We hypothesised that associations between adiposity and hypertension would be stronger, or more detectable, using body fatness assessed by DDM rather than BMI. The study involved 206 girls aged 13-19 years and 207 women aged 20-40 years. High BMI was defined as a BMI-for-age z-score of ≥ 2.00 for
adolescents, and BMI ≥ 30.0 kg/m² for adults. In adolescents, high body fatness was defined as a percentage body fat ≥ 30%, and in adults defined as ≥ 38% body fat. Elevated BP was defined as ≥120 mm Hg (systolic) with > 80mm Hg (diastolic). In adolescents, high BMI-for-age was only marginally significantly associated with elevated BP [X² (df=1) = 3.74, p=0.052], and excessive body fatness related insignificantly [X² (df=1) = 1.63, p=0.20] with hypertension. In the adults, both high BMI and elevated body fatness were significantly associated with hypertension [X² (df=1) =14.3, p<0.01]. Excessive body fatness assessed by DDM yielded no added value compared to high BMI in identifying associations between adiposity and hypertension in adolescent and adult Namibians.