Abstract
Although accounting for a striking proportion of obesity effects on blood pressure (BP) in other populations, the extent to which obesity-associated increases in BP are explained by insulin resistance and metabolic changes in populations of African ancestry is uncertain. We determined the contribution of insulin resistance and associated metabolic abnormalities to variations in office or ambulatory BP in a black African community with prevalent obesity and hypertension. In 1225 randomly selected participants of black South African ancestry (age>16years, 43.1% obese, 47.4% abdominal obesity), we assessed adiposity indexes, the homeostasis model of insulin resistance (HOMA-IR) and associated metabolic abnormalities and office or ambulatory (n = 798) BP. In separate models, waist circumference (p < 0.0005-<0.0001) and HOMA-IR (p < 0.51-0.005), were independently associated with office, 24 h, day or night systolic (SBP) or diastolic (DBP) BP. However, whilst a one standard deviation increase in waist circumference translated into a 1.47-3.08 mm Hg increased in office, 24-h SBP or DBP, in mediation analysis HOMA-IR accounted for only 0.12-0.30 mm Hg of the impact of a one standard deviation effect of waist circumference on office, and 24-h SBP and 0.003-0.17 mm Hg of the impact of a one standard deviation effect of waist circumference on office and 24-h DBP. In conclusion, in a black African community, insulin resistance accounts for a negligible proportion of the impact of obesity on office or ambulatory BP.