Circulatory responses to lower body negative pressure in young Afghans and Danes: implications for understanding ethnic effects on blood pressure regulation

• Published in: European journal of applied physiology Vol. 114; no. 11; pp. 2321 - 2329
• Main Authors: Asmar, Ali, Bülow, Jens, Simonsen, Lene, Rasmussen, Jonas G., Christensen, Niels J., Frandsen, Erik, Norsk, Peter
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-11-2014; Springer Nature B.V
• Subjects: Adult; Asian Continental Ancestry Group; Baroreflex; Biomedical and Life Sciences; Biomedicine; Blood Pressure; Cardiac Output; Cultural differences; Denmark; European Continental Ancestry Group; Hemodynamics; Human Physiology; Humans; Hypotheses; Immigration; Male; Males; Nuclear medicine; Occupational Medicine/Industrial Medicine; Original Article; Orthostatic Intolerance - ethnology; Pharmacists; Physiology; Plasma; Questionnaires; Sports Medicine; White people; Denmark; United States > US; Ethnicity; Orthostatic stress; Renin; Cardiac output; Noradrenaline
• ISSN: 1439-6319; 1439-6327
• DOI: 10.1007/s00421-014-2946-2

Purpose
We have previously shown that Afghans residing in Denmark for at least 12 years exhibit a lower 24-h ambulatory blood pressure compared to Danes. The purpose of this study was to test the hypothesis that the lower blood pressure reflects attenuated compensatory baroreflex responses in the Afghans.
Methods
On a controlled diet (2,822 cal/day, 55–75 mmol + 2 mmol Na+/kg/day), 12 young males of Afghan (Afghans) and 12 young males of Danish (Danes) origin were exposed to a two-step lower body negative pressure (LBNP) protocol of −20 and −50 mmHg, respectively, each of 10-min duration.
Results
Afghans had lower 24-h systolic blood pressure compared to Danes (115 ± 2 vs. 123 ± 1 mmHg,
p
 < 0.05). Cardiac output and stroke volume were significantly lower in Afghans compared to Danes prior to and during each level of LBNP. However, it decreased to the same extent in both groups during LBNP. During LBNP of −20 mmHg, plasma noradrenaline concentration and plasma renin activity (PRA) increased significantly only in the Afghans. At LBNP of −50 mmHg plasma noradrenaline concentration and PRA both increased significantly and similarly in the two groups.
Conclusion
The lower 24-h ambulatory blood pressure in the Afghans is probably caused by a lower stroke volume, which augmented the circulatory and vasoactive hormonal responses to LBNP in the Afghans. The lower stroke volume in Afghans residing in Denmark compared to that of matched native Danes remains to be explained.