Cardiovascular function, coping and cortisol in urbanised Africans : the SAPBA [i.e. SABPA] study

Abstract

Motivation: Environmental stressors have psychological and biological effects and the inability to cope with the stressor affects the mood and could lead to cardiovascular disease (CVD). Chronic stress leads to deregulation of hypothalamic pituitary adrenal axis (HPAA) which leads to increased circulating adenocorticotropic hormone (ACTH), cortisol, impaired feedback regulation of the axis and impaired glucocorticoid receptor binding in the hippocampus. Stress and related health impairments are major problems in human life, therefore, the investigation into the psychobiological pathways that link stress and disease are of great importance. Aim: The aim of the study was to assess the relationship between cardiovascular, cortisol and coping responses in urbanised Africans as well as its contribution towards progression of target organ damage. Methodology: The SABPA (Sympathetic Activity and Ambulatory Blood Pressure in Africans) study was a target population study which included a sample of fasting urban black Africans, aged 21-62 years, from one of four education districts in the Dr Kenneth Kaunda Education districts, North-West Province. There was a total of 200 fasting participants (N=101 men, N=99 women). Blood pressure (BP) measures according to the RoccilKorotkoff method were taken, followed by Finometer BP data, resting blood and saliva sampling before stressor application. Stressors included: the cold pressor test (CPT) and colour word conflict test (CWC). Cortisol saliva sample analysis was done with an enzyme-linked immunosorbant assay. Resting salivary cortisol levels were taken 45 minutes after awakening, avoiding the Cortisol Awakening Response (CAR), and completed before 10am according to standardized procedures. Cortisol sampling time 1 was between 06h30-07hOO and time 2 between 08h30-09hOO. Saliva cortisol sampling was done 30 minutes after exposure to each stressor (Salivette Sarstedt®). A winged infusion set was used, by a registered nurse, to sample blood from brachial vein branches; for serum estrogen as well as sodium fluoride glucose. The Coping strategy indicator (CSI), which has been has been successfully used in South Africa, was used. The CSt is a factor analytical derived measure of coping where three fundamental coping strategies are revealed: Problem solving, seeking social support and avoidance. The Ethics Committee of North-West University, Potchefstroom Campus, approved the study. Results: More men than women (63%; 34%) respectively are hypertensive. Hypertensive (HT) men show increased vascular responses when subjected to the cold pressor test (CPT) and HT women show similar vascular reactions, but only to the colour word conflict test (CWC) test. Irrespective of blood pressure (BP) status, men and women have high-normal blood glucose levels and high-normal cortisol values. Decreased cortisol reactivity is associated with the progression of target end organ damage in the HT men (p=0.06). Resting cortisol values in both men and women are significantly lower during sampling time 2, (p.=:: 0.001). Partial correlations, adjusted for age, BMI and cortisol sampling time, indicate that high problem solving as well as high avoidance correlates with central BP response changes during the CPT in HT men. Neck circumference (NC) and high problem solving correlate with central increases in BP in HT women during the CWC test. None of the coping strategies are associated with the progression of target end organ damage in either the men or the women. HT women are more centrally obese than their NT counterparts, and even than the HT men. Despite this, obesity is not associated with the progression of target end organ damage in the HT African women. Interestingly glucose and central obesity is positively associated with the progression of target end organ damage in the men. Conclusion: Glucose and central obesity is positively associated with the progression of target end organ damage and atherosclerosis in HT men. Decreased cortisol reactivity is associated with the progression of target end organ damage in the men, indicating possible HPPA hypoactivity due to chronic stress. However more research is needed to confirm this speculation. Coping strategies did not seem to be associated with progression of target end organ damage.