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: B¼34.99, P¼0.017; diastolic blood pressure: B¼34.93, Po0.001; total peripheral resistance reactivity: B¼65.44, P¼0.048; stroke volume reactivity: B¼À45.40, P¼0.017). 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.

Exploring the Link Between Cardiovascular Reactivity and End-Organ Damage in African and Caucasian Men: The SABPA Study

“…Because a reactivity pattern of a peripheral alpha-adrenergic nature was found, Ca 2+ -channel blockers, in addition to alpha-blockers, may be effective to relieve peripheral wall stress. 2,6 This may contribute to reduced afterload, which would consequently prevent impairment of the left ventricular ejection function. In addition, because our results showed no ethnic differences in resting SV (and only a small difference in resting vascular resistance) but great differences in reactivity patterns, we suggest that more research be conducted on cardiovascular reactivity patterns.…”

“…This may be due to several conditions occurring simultaneously over a long period, including changes in the arterial extracellular matrix, calcium sensitivity of the peripheral arteries, high α1-adrenergic receptor density, low plasma renin levels, sodium sensitivity, genetic differences, and other endocrine or paracrine factors. 2,[6][7][8][9]36 The increased peripheral vascular resistance response in Africans compared with Caucasians seems to play an important role in the development of hypertension. 13,37,38 Africans may be prone to early vascular aging genetically or as a result of environmental factors.…”

“…[16][17][18][19][20][21][22] It was reported that vascular resistance reactivity in Africans was positively associated with higher α1-adrenergic receptor density and therefore a higher serum calcium sensitivity. [6][7][8][9] This may explain the proposed increased vascular resistance that may be characteristic in Africans. 2 Another possible explanation is the higher arterial stiffness observed in populations of African descent, which may prove to be significant with regard to the development of hypertension in Africans.…”

“…2 It has been found that the pulse wave velocity (PWV) of muscular arteries is higher in young Africans compared with Caucasians and that there are increased levels of vascular resistance during stress. 6,[13][14][15] Increased reactions to acute psychological stress challenges are implicated in cardiovascular disease: inter alia hypertension, carotid atherosclerosis, and cardiac hypertrophy. [16][17][18][19][20][21][22] It was reported that vascular resistance reactivity in Africans was positively associated with higher α1-adrenergic receptor density and therefore a higher serum calcium sensitivity.…”

Plasma total calcium concentration is associated with blood pressure and systemic vascular resistance in normotensive and never-treated hypertensive subjects

“…In most of the earlier studies, the haemodynamic components involved in BP regulation were not addressed (Supplemental Table 1). However, Schutte et al [41] investigated the associations of serum total calcium concentration with 24-h ambulatory BP and Finometer V R measurements during a stress test in 99 African men. They found that in younger men (<43 years, n ¼ 50), but not in older men, serum total calcium concentration was directly associated with 24-h ambulatory BP and total peripheral resistance during the stress test [41].…”