title: Serum calcium revisited: associations with 24-h ambulatory blood pressure and cardiovascular reactivity in Africans.
abstract: 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.
authors.affiliation: Hypertension in Africa Research Team (HART), School for Physiology, Nutrition, and Consumer Sciences, North-West University (Potchefstroom Campus), Potchefstroom, South Africa. rudolph.schutte@nwu.ac.za
authors.forename: Rudolph
authors.initials: R
authors.lastname: Schutte
authors.forename: Hugo W
authors.initials: HW
authors.lastname: Huisman
authors.forename: Aletta E
authors.initials: AE
authors.lastname: Schutte
authors.forename: Nicolaas T
authors.initials: NT
authors.lastname: Malan
authors.forename: Johannes M
authors.initials: JM
authors.lastname: van Rooyen
authors.forename: Carla Mt
authors.initials: CM
authors.lastname: Fourie
authors.forename: Leoné
authors.initials: L
authors.lastname: Malan
mesh_terms: D000328:Adult; D000368:Aged; D044383:Black People; D001794:Blood Pressure / Q000502:physiology*; D018660:Blood Pressure Monitoring, Ambulatory; D002118:Calcium / Q000097:blood*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013019:South Africa; D013318:Stroke Volume / Q000502:physiology; D014655:Vascular Resistance
chemical_list: D002118:Calcium