Motivation: The different coping styles used to respond to psychosocial stress have been linked to the development of cardiovascular disease (CVD). However, the manner in which the cardiovascular system is influenced differs between the coping styles. Of the different coping styles, defensive active coping (AC) has been shown to be the most detrimental to cardiovascular health. This is worsened by augmented α-adrenergic cardiac responses found in Africans. Furthermore, many studies have found that the prevalence of hypertension and other CVDs is much higher in urban Africans when compared to their Caucasian counterparts. This can be attributed to certain lifestyle changes implemented by Africans in the transition that occurs with urbanization, where they are forced to cope with an urban-dwelling lifestyle. One of these lifestyle factors, which also poses as a cardiovascular risk factor, is increased usage and in some cases abuse of alcohol. Certain discrepancies exist between ethnicities with regard to the metabolism of alcohol, which influences the effect of alcohol on the individual. Alcohol usage as a possible manner of coping has been supported in many instances, but the interdependent effects of alcohol usage and AC as cardiovascular risk factors has only been found in African men. Further investigation is needed to determine if coping and alcohol abuse act in tandem only in African men, or also in other ethnic or sex groups. What also needs to be discussed is whether the inconsistencies between ethnicities regarding alcohol metabolism, plays a part in the development of CVD in a bi-ethnic gender cohort.
Objectives: The main aims of this study were to determine 1) receiver operated characteristic (ROC) ethnic specific cut points of alcohol usage in the prediction of ambulatory hypertension, and 2) to assess if these cut points in defensive active groups
revealed increased cardiometabolic risk in a bi-ethnic sex cohort, and if so, whether the increased risk will be associated with a specific race or sex group?
Methodology: This sub-study forms part of the SABPA (Sympathetic activity and Ambulatory Blood Pressure in Africans) study, conducted from 2008 to 2009. After exclusion criteria were applied, our bi-ethnic sex cohort consisted of 390 individuals. These participants were all from the Kenneth Kaunda Education District of the North-West province in South Africa, and they all signed informed consent prior to participation. The SABPA study was approved by the Ethics Review Board of the North-West University, with additional ethical approval for this sub-study. All procedures in this study complied with the guidelines of the Declaration of Helsinki.
Each participant completed a psychosocial battery supervised by registered clinical psychologists, and information regarding their medication use and medical history was obtained. They also completed the Coping Style Indicator questionnaire which was developed by Amirkhan, to identify the coping style habitually used. Ambulatory blood pressure and ECG measurements were recorded for a 24h period with the Cardiotens CE120®. Anthropometric measurements were performed by ISAK (International Society for the Advancement of Kinanthropometry) level 2 accredited anthropometrists using calibrated instruments. Out of this, the body surface area were calculated. The physical activity of each participant was determined by use of the Actical® omnidirectional accelerometer. Resting blood samples were collected by a registered nurse. The following blood serum levels were determined: gamma-glutamyl transferase (γ-GT) as a marker for alcohol usage, C-reactive protein, cholesterol, high density lipoprotein, triglycerides, cotinine, reactive oxygen species and glycated haemoglobin levels. All statistical analyses were done using Statistica version 12.0. Descriptive statistics were conducted to state the baseline characteristics of the entire group, while Chi-square (X2) tests were used to determine prevalence for medications and pathology. ROC analyses were computed to establish a cut point for γ-GT predicting ambulatory hypertension in each ethnicity as well as in the entire group. Independent t-tests
identified confounders, after which two-way analysis of covariance (ANCOVA) tests were computed to test a 2 x 2 main effects interaction (race x γ-GT cut points) for all cardiometabolic risk markers and to compare the different ethnic groups. ANCOVAs were then performed in the ethnic groups with high γ-GT as well as in above mean AC for the graphs that followed. Lastly, odds ratios (OR‟s) with 95% confidence intervals (CI‟s) were calculated in several models to highlight the odds of high alcohol intake to predict ambulatory hypertension in the ethnic-sex groups as well as in AC ethnic-sex groups. Significant values were noted as p ≤ 0.05.
Results: The Africans revealed higher cardiometabolic risk markers, above mean defensive active coping, seeking social support with less avoidance coping scores. ROC analyses revealed that ambulatory hypertension commences at a much higher level of γ-GT in the Africans [55.7U/l (AUC=0.69; 95% CI: 0.61; 0.76)] with sensitivity /specificity of 47%/83% compared to the Caucasians [19.5U/l (AUC=0.747; 95% CI: 0.68; 0.82)] with sensitivity/specificity of 70%/73%. The Caucasians thus reveal an increased sensitivity for alcohol ingestion at a much lower γ-GT cut point compared to the Africans.
When comparing ethnic specific ROC cut point groups, we found that certain levels of cardiometabolic risk factors such as C-reactive protein, systolic blood pressure, waist circumference and silent ischemic events, were significantly higher in the African group, especially in above mean AC groups. Out of the Africans with high γ-GT levels, 73% used the AC style, suggesting hypervigilant AC coping and increased CVD risk in Africans.
Clinical significance was determined by OR‟s, which demonstrated that high γ-GT levels in AC African men predicted ambulatory hypertension with an OR of 7.37 (95% CI: 6.71 – 8.05). Higher alcohol intake predicted ambulatory hypertension in AC Caucasians with an OR of 2.77 (95% CI: 2.31 – 3.23) in men and 6.42 (95% CI: 5.85 – 7.0) in women respectively.
Conclusion: γ-GT cut-points in defensive active groups revealed increased cardiometabolic risk markers in a bi-ethnic sex cohort. A possible hypermetabolic state in African men may initially protect them against CVD morbidity but if chronically challenged with no forthcoming social support, CVD risk is imminent. / MSc (Physiology), North-West University, Potchefstroom Campus, 2015
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/15493 |
| Date | January 2014 |
| Creators | Oosthuizen, Woudri |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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