Differences in Resting Cardiovascular Parameters in 10- to 15-Year-Old Children of Different Ethnicity: The Contribution of Physiological and Psychological Factors Johannes M. van Rooyen, D.Sc. School for Physiology, Nutrition and Consumer Sciences Potchefstroom University Alida W. Nienaber, Ph.D. School for Psychosocial and Behavioral Sciences Potchefstroom University Hugo W. Huisman, Ph.D., Aletta E. Schutte, Ph.D., Nico T. Malan, D.Sc., Rudolph Schutte, M.Sc., and Leonè Malan, M.Sc. School for Physiology, Nutrition and Consumer Sciences Potchefstroom University ABSTRACT Background: The health status of children in the North West Province of South Africa was examined using the Transi- tion and Health during Urbanization in South Africa in Chil- dren study. This is an epidemiological, cross-sectional study for which 1,244 children between 10 and 15 years of age were re- cruited from 44 schools. Purpose: Our objective was to investi- gate whether differences exist between resting cardiovascular parameters of Black, White, colored, and Indian children and evaluate the contribution of physiological and psychological factors. Methods: Blood pressure was monitored with the Finapres apparatus. By means of the Fast Modelflo software program, the systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure, heart rate, cardiac output (CO), total peripheral resistance (TPR), and “Windkessel” compliance (Cw) of the arterial system were obtained. The psychological data were obtained by validated questionnaires. Results: After correction for body mass index, the SBP of the White children was significantly higher (p < .05) than the SBP of the other eth- nic groups. The DBP showed no significant differences. The TPR measurements of the Black and colored children were sig- nificantly higher (p < .05) than the TPR of the White children, and the Cw measurements of the Black and colored children were significantly lower than the Cw of the White children. Sig- nificant correlations (p < .05) were found between the SV, CO, TPR, Cw, and the total score on violence in the Black and col- ored children. Conclusions: There are differences in the resting cardiovascular parameters in the different ethnic groups stud- ied. The higher levels of violence to which the Black and colored children are exposed could alter vascular sensitivity to sympa- thetic stimulation. This may contribute via the higher α-adren- ergic sensitivity to the pathogenesis of hypertension in their later lives. (Ann Behav Med 2004, 28(3):163–170) INTRODUCTION In the South African population of just over 43 million in 2000, the population comprises 77.6% Africans (Black), 2.5% Asians (Indian), 8.7% coloreds (people of mixed origin), and 10.4% Whites (European) (1). Clear differences in the preva- lence of hypertension have been observed between the different adult population groups. These different ethnic groups indicate hypertension prevalence that varies from 14.2% in Indians, 17.2% in Whites (2), 22.2% average in Blacks to as high as 32.9% in Blacks living in informal settlements near the cities (3), and 30.2% in coloreds (4). Although clinical hypertension occurs less frequently in children than in adults, ample evidence supports the concept that the roots of essential hypertension extend back to childhood (5–7). Of particular importance is the documentation that ele- vated blood pressure in childhood often correlates with hyper- tension in early adulthood, thereby supporting the need to track blood pressure in children (8). Conflicting results have been re- ported in the literature regarding ethnic differences in blood pressure levels in children and adolescents (9,10). Findings from the Bogalusa (11) study and another study (12) showed that from late childhood onward, African Americans exhibit higher blood pressure levels than Caucasians. Studies of blood pressure in African American, Hispanic, and non-Hispanic chil- dren showed no consistent or statistically significant differences in blood pressure levels among children and adolescents, re- gardless of adjustment for weight or use of auscultatory or oscillometric methods (13,14). After application of physical stimuli (exercise, cold pressor, or postural tilt) in Black and White children, similar responses in blood pressure were found, but the mechanisms sustaining blood pressure elevations in 163 We thank the whole THUSA BANA research team and Professor H. S. Steyn of the Statistical Consultation Service of the Pot- chefstroom University for CHE. We also thank those who have funded this study: The SA Sugar Association, the Medical Research Council of South Africa, the Potchefstroom University for CHE, Hy- pertension Society of SA, and Department of Trade and Industry through the THRIP system. Reprint Address: J. M. van Rooyen, D.Sc., School for Physiology, Nutrition and Consumer Sciences, Faculty of Health Sciences, Pot- chefstroom University, Potchefstroom, South Africa, 2520. E-mail: flgjmvr@puknet.puk.ac.za © 2004 by The Society of Behavioral Medicine.