Coping, stress hormones and cardiovascular function in urbanised Africans
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Motivation: Urbanisation is now a more universal phenomenon than ever before. The negative effects of urbanisation on health, i.e. cardiovascular dysfunction, hypertension prevalence rates and endocrine patterns of stress are more prominently found in black Africans compared to white counterparts. The association between the underlying physiological and psychological mechanisms of this phenomenon, is however, still unclear. Objectives: The main objective of this study is to investigate the association between coping styles, stress hormones and cardiovascular function in rural and urban Africans. Methodology: This study is part of the "Transition and Health during Urbanisation in South Africa" (THUSA) study, a cross-sectional comparative epidemiological study, which ran from 1996-1998. Magistrate districts (37) in the North-West province was identified and randomly selected to be representative of all levels of urbanisation. The initial subject group consisted of 821 apparently healthy African men and women between the ages of 16 and 70 years. After removal of incomplete datasets, this study group consisted of 353 African men and women. Anthropometric measurements were taken with assistance from biokinetisists and questionnaires were completed with the help of trained field workers and qualified psychologists. Subjects were divided into an active coping (AC) group or passive coping (PC) group, dependent on their responses on the S-COPE questionnaire, which is a validated and reliable Setswana translated version of the original COPE questionnaire. The subjects were subsequently divided according to their level of urbanisation i.e. rural or urban groups. The rural group consisted of subjects from tribal areas and farmland dwellings who had limited access to water and electricity. The urban group consisted of blue-collar workers living on the peri-urban fringe of greater metropolitan areas, who had access to water and electricity. Resting blood pressure values were measured using the FlNApres method. Subjects were divided into normotensive and hypertensive groups in accordance with blood pressure values from the FlNApres method and Riva-Rocci/Korotkoff method. Fasting, resting serum stress hormone values of cortisol, prolactin and testosterone levels were measured and correlated with the cardiovascular values, dependent and independent of coping styles. Significant differences between the variables were determined with variance analyses independent of age, body mass index (BMI) and lifestyle factors i.e. physical activity, alcohol consumption and smoking habits. Informed consent was obtained from all the participants, with consent from parents of under-aged adolescents. The Ethics Committee of the Potchefstroom University for Christian Higher Education (PU for CHE) approved the study. The reader is referred to the abstract at the beginning of the manuscript in Chapter 3 for a description of the subjects, study design and analytical methods used in this paper. Results: Results from the THUSA study indicated that the urbanised subject group were younger and physically more active but with higher levels of alcohol consumption and hypertension prevalence rates than their rural counterparts. Urbanised men also revealed a cardiovascular pattern of higher vascular activity - total peripheral resistance (TPR), lower cardiac output (CO) and compliance (CO) but with higher heart rate compared to rural subjects. The endocrine profile of urbanised men revealed higher prolactin and lower testosterone values, coupled to smaller cortisol:prolactin and larger cortisol:testosterone values. Urbanised women revealed a similar pattern of higher vascular activity (higher diastolic blood pressure values (DBP) and TPR values, with lower CO and Cw) and prolactin values when compared to rural women. When coping styles were added into the equation, the AC urbanised men revealed a pattern similar to all urbanised men in regards to lifestyle factors, blood pressure values and hipertension prevalence rates . Additionally, they revealed higher heart rates and lower Cw values coupled to larger prolactin and smaller testosterone values as well as a larger cortisol:prolactin relationship. Urbanised AC and PC women had higher alcohol consumption values and higher vascular activity, with only AC women revealing higher hypertension prevalence rates compare to their rural counterparts. Only PC urbanised women revealed higher prolactin values and physical activity levels compared to their rural counterparts. Conclusion: Urbanisation in Africans can be associated with a poorer cardiovascular and a greater stress experiencing pattern compared to rural subjects. This pattern is more accentuated in AC urbanised men, who showed signs of chronic stress and a larger cortisol:prolactin ratio.
- Health Sciences