Twenty-four hour ambulatory blood pressure reference values in Africans.

OBJECTIVE: We aimed to establish reference values for 24 h ambulatory blood pressure (ABP) monitoring in an African community. PATIENTS AND METHODS: We randomly recruited 1219 participants of African ancestry from Soweto, a township in Johannesburg. Twenty-four hour ABP was measured using ABP monitors (model 90207; Spacelab). Complete 24 h ABP measurements from 530 healthy participants with a mean age of 38 were used to determine thresholds. RESULTS: Twenty-four hour, daytime and night-time systolic and diastolic BP increased significantly with age. The 95th prediction bands of this relation at age 38 years were ∼135/85 mmHg for 24 h, 140/90 mmHg for daytime and 130/80 mmHg for night-time ABP values, respectively. These thresholds and absolute ABP values are similar to those observed in individuals of other demographics. These thresholds increase with age by an average of 1.5 mmHg with each decade's increase in age. CONCLUSION: Pending authentication in prospective outcome-based studies, these values might be considered preliminary thresholds to diagnose hypertension in individuals of African descent.

Obesity masks the relationship between dietary salt intake and blood pressure in people of African ancestry: the impact of obesity on the relationship between sodium and blood pressure.

Previous studies conducted to investigate the relationship between sodium intake and blood pressure in our African population have yielded contradictory results. With the high prevalence of obesity in this population, it is possible that these contradictory findings are due to the masking effects of obesity on this relationship. We measured 24-hour ambulatory blood pressure and 24-hour urine excretion on 547 South Africans of African ancestry. A multivariate regression analysis revealed no independent relationship between 24-hour sodium excretion and blood pressure in the total population sample, but when participants were stratified according to body mass index (BMI) status, there was a significant association between 24-hour sodium excretion and blood pressure in the normal-BMI participants but not in the overweight/obese participants. We concluded that dietary salt intake, indexed by 24-hour urinary sodium excretion, was associated with increased ambulatory blood pressure but this relationship was masked because of a high proportion of overweight/obese individuals in this population.