title: Cardiovascular reactivity in Black South-African males of different age groups: the influence of urbanization.
abstract: OBJECTIVE
  Blacks in an urban environment seem to be more vulnerable to excessive increases in blood pressure during daily life events. This greater cardiovascular reactivity during acute stress situations in urban Blacks may lead to the development of hypertension in their later lives. Because Blacks in South Africa are involved in a massive process of urbanization, which may lead to chronic diseases of lifestyle like hypertension and diabetes, this study was undertaken to compare the cardiovascular reactivity patterns of urbanized and rural Black males in the North-West province of South Africa.
  
  
  METHODS
  Two hundred twenty-three Black males of different age groups, Group 1: younger than 25 years of age; Group 2: between 25 and 44 years of age; and Group 3: 45 years of age and older. Participants were randomly selected from rural and urbanized settlements.
  
  
  METHODS
  After resting blood pressure was recorded with a Finapres apparatus, and cardiac output, stroke volume, heart rate, and total peripheral vascular resistance had been obtained, an acute laboratory stressor (hand dynamometer exercise) was applied and the above measurements repeated.
  
  
  RESULTS
  The SBP, DBP, and MAP increased 28% and 42% in both the rural and the urbanized groups. There was a shift from a central reactivity pattern (increased cardiac output) in the young rural group (< 25 years) to a peripheral reactivity pattern (increased total peripheral resistance) in the > or = 45 years old urbanized males after applying the stressor.
  
  
  CONCLUSIONS
  Cardiovascular reactivity differs between Black males from a rural area compared to urbanized Black males. The urbanized males > or = 45 years of age were at a higher risk of developing cardiovascular disease because their total peripheral resistance reactivity increased the most during application of the stressor.
authors.affiliation: School for Physiology, Nutrition and Consumer Science, Section Physiology, Potchefstroom University for CHE, South Africa. flgjmvr@puknet.puk.ac.za
authors.forename: J M
authors.initials: JM
authors.lastname: van Rooyen
authors.forename: H W
authors.initials: HW
authors.lastname: Huisman
authors.forename: F C
authors.initials: FC
authors.lastname: Eloff
authors.forename: P J
authors.initials: PJ
authors.lastname: Laubscher
authors.forename: L
authors.initials: L
authors.lastname: Malan
authors.forename: H S
authors.initials: HS
authors.lastname: Steyn
authors.forename: N T
authors.initials: NT
authors.lastname: Malan
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000704:Analysis of Variance; D044383:Black People / Q000235:genetics*; D001795:Blood Pressure Determination; D002318:Cardiovascular Diseases / Q000208:ethnology* / Q000503:physiopathology*; D002320:Cardiovascular Physiological Phenomena; D015331:Cohort Studies; D005080:Exercise Test; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D006973:Hypertension / Q000208:ethnology* / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012016:Reference Values; D018570:Risk Assessment; D012424:Rural Population; D013019:South Africa / Q000453:epidemiology; D014507:Urbanization; D014655:Vascular Resistance