Motivation: Cardiovascular dysfunction and hypertension are some of the leading causes of
morbidity and mortality in the African population. According to the World Health Organisation the
increases in these diseases are escalating in developing countries. Apart from the contributory
role of genetics towards the incidence of hypertension, evidence regarding lifestyle as a
determinant or marker of cardiovascular diseases in this group is not well known. The
interaction of psychological and physiological mechanisms can contribute towards a broader
scope of behavioural physiology in the higher prevalence of hypertension in Africans.
Objectives: The main objective of the research in this thesis was to compare specific coping
mechanisms of Africans with regard to cardiovascular dysfunction.
Methodology: Manuscripts presented in Chapters 3, 4, and 5 made use of the cross-sectional
comparative epidemiological "Transition and Health during Urbanisation in South
Africa" (THUSA) project. The subjects included apparently healthy African men and women,
which were recruited as a convenience sample from the North West Province, South Africa.
Anthropometric measurements were taken and demographic questionnaires completed. An
adapted Setswana COPE questionnaire was used to classify men and women as predominantly
active (AC) or passive (PC) in coping style. Subjects were further subdivided into rural and
urban groups (Manuscript Two), as well as younger (≤ 40) and older (≥ 45) age groups
(Manuscript Three). The General Health Questionnaire (GHQ) was used to measure subjective
perception of health in all three manuscripts. Blood pressure was recorded continuously before
and during application of the handgrip test using the Finapres apparatus. Subjects were
classified as normotensive and hypertensive after blood pressure measurement by the Finapres
and the Riva-Rocci/Korotkoff method. The emphasis in this study was on the cardiovascular
reactivity values. Fasting, resting serum renin activity, cortisol, prolactin, testosterone, high
density lipoprotein, triglycerides, glucose and plasma fibrinogen values were correlated with
cardiovascular and psychological variables. Significant differences between variables were
determined by means of variance analyses (Manuscript One and Two adjusted for age;
Manuscripts One, Two and Three adjusted for resting cardiovascular data). A logistic regression
analysis was performed to determine the most significant determinants of urbanisation. All
THUSA subjects and parents of under-aged adolescents gave informed consent and the study
- was approved by the Ethics Committee of the Potchefstroom University for Christian Higher
Education. The reader is referred to the abstracts at the beginning of each separate manuscript
in Chapters 3 - 5 for a description of the subjects, study design and analytical methods used in
each paper.
Results and conclusions of the individual manuscripts:
Results from the THUSA study showed that PC men and women reported more symptoms
typical of an abnormal psychological and physiological profile than AC men and women. The
PC men, compared to AC men, exhibited a larger vascular reactivity response as well as
larger plasma renin activity. In contrast, the AC women showed a larger non-significant
vascular reactivity response than PC women. All subjects though reacted with increased
vascular reactivity on the stressor. Men with a PC strategy showed enhanced vascular
reactivity, a perception of poorer health and larger stressor plasma renin activity. PC women
reported more depressive symptoms and younger PC women indicated a higher prevalence
of hypertension than younger AC women.
As a follow-up on the first manuscript, the aim was focused mainly on including the
environmental effect, namely urbanisation, as possible explanatory factor for the atypical
physiological AC women’s' coping style. The rural AC subjects indicated more typical active
coping central cardiac responses than rural PC subjects whereas urbanised AC and PC
subjects indicated greater peripheral responses and hypertension prevalence rates. In
addition, the urbanised AC men and women and PC women as opposed to their rural
counterparts indicated symptoms more of a distress situation with increased values of
prolactin and decreased values of testosterone. This was also accompanied by a perception
of poorer health in women. Results of the AC style suggests that the typical physiological
AC stimulation pattern of urbanised subjects and especially the women is dissociated from
the "normal" physiological AC reaction and is now exhibited as a typical PC physiological
stimulation pattern. The greater vascular reactivity, hypertension prevalence, perception of
poorer health and endocrine distressed profile are associated with a PC and dissociated
physiological AC style in an urban context in African men and women. No differences with
regard to resting blood pressure or endocrine values were obtained when the AC and PC
urbanised groups were compared. Africans develop cardiovascular
dysfunction/hypertension during chronic stress or urbanisation. This implies a
dissociation/habituation of physiological systems of African men and women despite having
an active coping strategy. Active coping is, therefore, not necessarily "successful".
Results of the first two manuscripts direct further investigation concerning the effects of
ageing and urbanisation on the development of cardiovascular dysfunction and metabolic
syndrome indicators in gender groups. The second manuscript showed that all rural AC
subjects exhibit a more typical active coping central cardiac response and that rural PC and
all urbanised subjects (AC and PC) exhibit enhanced peripheral vascular responses on the -
handgrip test. Where peripheral vascular responses were more expected from older
individuals in Manuscript Three, the occurrence of this pattern is strengthened in the younger
subjects. The greater fibrinogen values in all younger urbanised women (AC and PC)
compared to rural women further strengthen the risk for the development of cardiovascular
disease. Increased vascular reactivity, abdominal obesity and increased levels of
triglycerides as well as perception of poorer health were apparent in the urbanised AC
women, PC men and women in comparison to their rural counterparts. The typical
physiological AC stimulation pattern of urbanised women is dissociated from the "normal"
physiological AC responses and is now exhibited as a typical PC physiological stimulation
pattern. A typical PC style in older urbanised subjects is implicated in the greater
hypertension prevalence.
To conclude, it seems as if young urbanised Africans, and especially women, exhibit an AC
style behaviourally with a dissociated physiological AC reaction pattern. Physiologically these
women resemble a typical PC physiological cardiovascular and endocrine profile. This typical
PC cardiovascular stimulation pattern is strengthened by a distressed endocrine profile,
significant metabolic syndrome indicators and a 'perception of poorer health. Older PC style
subjects also presented a greater hypertension prevalence. In this study it seems that
cardiovascular changes that appear at a younger age might be influenced by other factors
including urbanisation as a lifestyle factor as well as specific coping styles. Finally, a careful
suggestion is made that specific coping mechanisms could be seen as a possible risk marker in
the development of the metabolic syndrome. / Thesis (Ph.D. (Physiology))--North-West University, Potchefstroom Campus, 2005.
| Identifer | oai:union.ndltd.org:NWUBOLOKA1/oai:dspace.nwu.ac.za:10394/767 |
| Date | January 2005 |
| Creators | Malan, Leoné |
| Publisher | North-West University |
| Source Sets | North-West University |
| Detected Language | English |
| Type | Thesis |
Page generated in 0.0028 seconds