The relationship between baroreflex sensitivity and cardiovascular function in Africans and Caucasians from South Africa : the SAfrEIC study

Abstract

In the past four decades Africans from Sub-Saharan Africa has become more westernised due to increasing urbanisation. Along with this came changes in lifestyle and diet, which consequently led to the increased prevalence of non-communicable diseases, especially cardiovascular disease. This upward trend in the prevalence of cardiovascular diseases in Sub-Saharan Africa is observed with hypertension being the most prominent. Caucasian-based studies indicate that reduced baroreflex sensitivity, which is an imbalance in the autonomic nervous system with a shift to the sympathetic side, is linked to the onset of hypertension. It is unclear whether this also has a contributing role in the increased hypertension prevalence observed in Africans. The study was embedded in the SAfrEIC (South African study regarding the influence of Sex, Age and Ethnicity on Insulin sensitivity) study that included 747 African and Caucasian men and women living in the Potchefstroom region of the North West Province of South Africa. The inclusion criteria were apparently healthy participants aged 20-70 years. The exclusion criteria were pregnancy, lactation and diabetes (type 1 or 2 as well as the use of diabetic medication). Participants were divided into four groups: African women (n = 192); African men (n = 181); Caucasian women (n = 211) and Caucasian men (n = 163). Weight, height and waist circumference were measured with a precision Health Scale, A & D Company, Japan; Invicta Stadiometer, IP 1465, UK; Holtain unstretchable metal tape, respectively. Blood pressure was measured with a Finometer device (FMS, Finapres Measurement Systems, Arnhem, The Netherlands). The Beatscope 1.1 software programme integrated the data of each participant (age, gender and height). Blood pressure of the participants was also measured with the validated OMRON Model HEM-757. Pulse wave velocity, as an indicator of arterial stiffness was measured with the Complior SP apparatus. Baroreflex sensitivity was determined by the validated cross-correlation baroreflex sensitivity (xBRS) method, derived from the continuous blood pressure measurement using the Finometer apparatus. Serum total cholesterol and gamma glutamyltransferase were analyzed with the Konelab TM auto analyzer (Thermo Fisher Scientific Oy, Vantaa, Finland), while low-density lipoprotein was computed according to the Friedewald-formula. The main finding of the study was that baroreflex sensitivity decreased with increasing pulse wave velocity, indicating a contributing role of arterial stiffness to decreasing baroreflex sensitivity. Although systolic blood pressure and pulse wave velocity was the highest in African men, no significant differences existed for baroreflex sensitivity between the groups. However, after adjusting for significant covariates, baroreflex sensitivity tended to decrease with increasing pulse wave velocity in African men only. To date, there are no studies that explored this specific relationship in Africans from South Africa. In conclusion, increased arterial stiffness possibly contributes to reduced baroreflex sensitivity in black South Africans.