The African Prospective study on the Early Detection and Identification of Cardiovascular disease and Hypertension (African-PREDICT): Design, recruitment and initial examination.

BACKGROUND: Globally hypertension is stabilising, but in sub-Saharan Africa the incidence of hypertension remains on an increase. Although this might be attributed to poor healthcare and ineffective antihypertensive treatment, there is a limited understanding of population and individual-specific cardiovascular pathophysiology - necessary for effective prevention and treatment strategies in Africa. As there is a lack of longitudinal studies tracking the early pathophysiological development of hypertension in black populations, the African-PREDICT study was initiated. The purpose of this paper is to describe the detailed methodology and baseline cohort profile of the study. METHODS AND RESULTS: From 2013 to 2017, the study included 1202 black ( N = 606) and white ( N = 596) men and women (aged 20-30 years) from South Africa - screened to be healthy and clinic normotensive. At baseline, and each 5-year follow-up examination, detailed measures of health behaviours, cardiovascular profile and organ damage are taken. Also, comprehensive biological sampling for the 'omics' and biomarkers is performed. Overall, the baseline black and white cohort presented with similar ages, clinic and 24-hour blood pressures, but black adults had lower socioeconomic status and higher central systolic blood pressure than white individuals. CONCLUSIONS: The prospective African-PREDICT study in young black and white adults will contribute to a clear understanding of early cardiovascular disease development.

Soluble urokinase plasminogen activator receptor and hypertension among black South Africans after 5 years.

Soluble urokinase plasminogen activator receptor (suPAR) is a biomarker that links inflammation with cardiovascular risk. However, studies linking suPAR and hypertension are scant. First, we determined whether baseline suPAR is elevated in normotensive black South Africans who developed hypertension over 5 years, compared with those who remained normotensive; and second, whether hypertension is associated with suPAR. This substudy is embedded in the South African leg of the Prospective Urban and Rural Epidemiology study, performed in the North West Province. We investigated 429 normotensive individuals, of which 191 developed hypertension and 238 remained normotensive over 5 years. We determined suPAR from plasma (ethylenediaminetetraacetic acid) samples with the suPARnostic ELISA Kit and blood pressure with an OMRON HEM-757 device. Despite similar mean baseline suPAR levels (P=0.43), suPAR increased more in the group that developed hypertension compared with those who remained normotensive (14.2% vs. 6.94%; P=0.007). Five-year percentage change in systolic blood pressure correlated positively (r=0.23; P=0.002) and associated independently with baseline suPAR (ß=0.14; P=0.043), only in participants who developed hypertension. Participants were 1.41 times more likely (P=0.015) to develop hypertension with 1 s.d. increase in percentage change in suPAR levels over 5 years. Change in systolic blood pressure was associated with baseline suPAR in hypertensive participants and change in suPAR with hypertensive status. This study highlights the need for more research on the role of suPAR in hypertension and cardiovascular disease development in black South Africans.

Serum calcium revisited: associations with 24-h ambulatory blood pressure and cardiovascular reactivity in Africans.

Sub-Saharan Africans face an increasing burden of hypertension. Although controversial, recent experimental evidence strongly suggests that serum calcium contributes to elevated blood pressure through increased vascular resistance. We investigated the associations of 24-h blood pressure and cardiovascular reactivity with serum calcium in African men stratified by age. The study consisted of 50 younger (median age: 38 years) and 49 older (median age: 49 years) participants. We measured 24-h ambulatory blood pressure with a mean successful inflation rate of 72.6%. Total peripheral resistance and stroke volume reactivity were obtained using a Finometer device during application of the Stroop color and word conflict test. Total serum calcium was adjusted for serum albumin. Results showed that serum calcium levels were similar between the younger and older groups. However, in the younger group, 24-h systolic blood pressure, 24-h diastolic blood pressure and total peripheral resistance reactivity correlated positively, whereas stroke volume reactivity correlated negatively with serum calcium in single and multiple regression analyses (systolic blood pressure: B=34.99, P=0.017; diastolic blood pressure: B=34.93, P<0.001; total peripheral resistance reactivity: B=65.44, P=0.048; stroke volume reactivity: B=-45.40, P=0.017). No associations were evident in the older African men. In conclusion, 24-h ambulatory systolic and diastolic blood pressures are positively associated with serum calcium in African men younger than 43 years. The blood pressure-serum calcium relationship seems to be mediated through increased vascular resistance during stress.