Relationship between socio-economic status and cardiovascular disease in black South Africans living in a rural and an urban community
Egbujie, Bonaventure Amandi
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Introduction: In recent years, cardiovascular disease (CVD) has emerged as a leading cause of death in developing countries. It is important to identify and target people who are at risk,given that a third of all deaths are expected to be due to CVD by 2020. Studies have shown socio-economic patterning in the prevalence of risk factors for CVD, including obesity,smoking and lipid profile. In developed countries, the association between socio-economic status (SES) and CVD risk factors is negative, with a higher prevalence of CVD risk factors among people of lower SES. However, findings from studies in developing countries on this including South Africa has been inconsistent. In addition, there is scant information on differences in socio-economic patterning of CVD risk factors between urban and rural areas in South Africa.Aim: To examine the association between SES indicators and CVD risk factors among an adult population cohort of Black South Africans living in a rural and urban community.Study design: Quantitative cross-sectional analytical study of baseline data of a populationbased cohort of 2000 Black South African men and women aged 30-70 years who are part of the Cape Town arm of the Prospective Urban and Rural Epidemiology (PURE) Study. The study cohort has been established in Mount Frere, Eastern Cape (rural) and Langa, Cape Town(urban) since 2009 and the current work is secondary analysis of the baseline study data.Data collection/synthesis: SES indicators including income, employment status, marital status and completed education were gleaned from the baseline data of the PURE Cape Town study for all study participants. Then CVD risk factors including obesity, hypertension, selfreported diabetes, consumption of tobacco and alcohol consumption were also determined for the same participants. Data analysis: Data was analysed using SPSS version 20 for Windows. Descriptive statistics including frequency counts, percentages, mean and standard deviations (where normal distribution) and median and interquartile range (where non-normal) were used to summarise data on SES and CVD risk factors. This was performed separately for rural and urban study participants. Analytical statistics was used to examine associations between SES indicators and CVD risk factors with risk factors as both dichotomous and multi-level categorical variables.Kendall’s τ rank correlation coefficient was obtained to assess the relationship between the three indicators of SES. Prevalence rates reported with 95% confidence intervals was determined for risk factors across categories of SES indicators. P-values for trends in CVD risk factors were obtained by treating the SES indicators as categorical variables in logistic regression analyses. Multiple logistic regression analysis to estimate independent effects of the different SES indicators on risk factors was performed. In all analyses, P-values< 0.05 were regarded as significant.Results: There was a significant difference in the socioeconomic and CVD risk factors profile of urban and rural participants. Except for hypertension and tobacco use with insignificant higher prevalence in the urban location, all CVD risk factors were significantly higher in urban than rural participants. Some CVD risk factors (hypertension and diabetes) were positively associated with high SES (income) and some others (tobacco use) were negatively associated with employment status. Highest income earners had the highest risk of hypertension (AOR= 2.4, 95% CI 1.5-3.9) and diabetes (AOR= 2.2, 95% CI 1.2-4.1) after adjusting for age, sex and other SES variables. Marital status however showed the most consistent association across all CVD risk factors; widowed participants had a high risk of hypertension (OR=2.1, 95% CI 1.2-3.7) and diabetes (OR=2.0, 95% CI 1.1-3.7), but had the lowest risk of tobacco (OR=0.3, 95% CI 0.14-0.66) and alcohol use (OR=0.3, 95% CI 0.15-0.72). The distribution of CVD risk factors by SES gradient showed inconsistent patterning and difference between the urban and rural participants.Conclusion: In this cohort of adult Black South Africans, high income earning and widowed marital status were associated with higher hypertension and diabetes prevalence, while unemployment was associated with higher tobacco use.Recommendations: CVD risk reduction interventions that recognise the differential susceptibility of individuals in different SES group need to be designed and implemented.Widows and widowers should be given focussed attention in health screening as they may have increased vulnerability to diseases especially CVDs. There is however need for more research to establish the pathway through which SES factors predispose or protect individuals from CVDs.