Analysing the socioeconomic determinants of hypertension in South Africa: A structural equation modelling approach

Includes bibliographical references.Epidemiological research has long since observed that the prevalence of hypertension varies across populations' socioeconomic strata. Higher socioeconomic status (SES) has been consistently associated with lower levels of blood pressure in most studies from Europe and North America, while research in low- and middle-income countries at an earlier stage of the epidemiological transition revealed mixed patterns. The causal mechanisms underlying these varying relationships are largely unknown. Only in recent years the pathways through which SES impacts the cardiovascular system have been explored in large-scale studies, with results suggesting that body mass index, heart rate, and to a lesser extent physical exercise, alcohol use and smoking, may play a role in mediating these associations. However, these results refer to high-income countries, while similar research in low- and middle-income countries, and sub-Saharan Africa in particular, is lacking. In 2008, the National Income Dynamics Study (NIDS) collected a broad range of information on a representative sample of the population of South Africa, a medium-income country undergoing rapid epidemiological transition. Among other topics, information was gathered on blood pressure, biologic and behavioural risk factors, education, income and other indicators of socioeconomic position

Understanding blood pressure dynamics in the South African population: a latent variables approach to the analysis and comparison of data from multiple surveys

Background: The 2015 edition of the Global Burden of Diseases Study identified elevated systolic blood pressure─ defined as systolic blood pressure greater than the minimum risk category of 110–115 mm Hg ─ as the largest single contributor to the global burden of disease, responsible for 211.8 million disability adjusted life years lost, up 8.8% in the last decade. Middle‐income countries are currently bearing the highest share of this burden, and, because of the rapid demographic transition towards larger and older populations, the burden is bound to increase rapidly in the coming years, unless age‐specific values of blood pressure are substantially reduced to compensate for the unfavourable demographic changes. Achieving this more favourable blood pressure distribution in populations undergoing rapid changes in their socioeconomic structure requires knowledge of the mechanisms underlying temporal variations of blood pressure and the relationships of such variations with socioeconomic variables.However, evidence on these mechanisms and reliable information on the temporal trends of blood pressure themselves are scant outside high‐income countries. Given the large gain in health that would result in low‐ and middle‐income countries if an optimal blood pressure were to be achieved in large sectors of the population, there is little doubt that temporal trends in the distribution of blood pressure in these populations and their possible determinants are an open and important area for investigation. Objectives: Objectives of the study were: 1. To assess the level of quality and comparability of blood pressure data collected in a series of large‐scale surveys carried out between 1998 and 2015 in South Africa, a middle‐income country undergoing rapid demographic and epidemiological transition; 2. To explore the possibility of applying a series of latent variables techniques to improve the comparability of data from the different sources and to minimise the effect of measurement and representation error on the estimation of cross‐sectional relationships and temporal trends; 3. To estimate changes in the distribution of blood pressure and derived quantities ‐‐‐ such as prevalence of uncontrolled hypertension ‐‐‐ in the South African adult population between 1998 and 2015, taking into account between‐surveys differences and measurement and representation error that could lead to artefactual conclusions; 4. To estimate the extent to which the estimated changes in the blood pressure distribution during the study period could be explained by concurrent changes in the distribution of a series of biological, behavioural and socioeconomic risk factors. Methods: A series of techniques within the general framework of structural equation modelling were applied to jointly analyse the data and estimate the temporal trends and relationships of interest. Results: The average systolic and diastolic blood pressure of South African adult women has progressively decreased since 2003‐2004, reversing the previous rising trend. Among men, the reversal happened only for the systolic blood pressure, while the average diastolic blood pressure continued rising, although at a lower pace than previously.In both genders, this pattern resulted in a reduction of the prevalence of uncontrolled hypertension between 2003‐2004 and 2014‐2015, by 8 percentage points among women and by 4.5 percentage points among men. This consistent and rapid decrease cannot be explained by changes in the age structure of the population, smoking and alcohol consumption habits, distribution of body mass index or urbanization. The diffusion of antihypertensive treatment and, among women, cohort effects and rapidly increasing educational level partly explain the recent trend, but a substantial part of the observed decrease remains unexplained by the factors available in our analyses. Large seasonal variations in both systolic and diastolic blood pressure are present in the South African population, and their magnitude is greater among population strata with low socioeconomic status. From a methodological point of view, there were two further results of this study. First, estimates of blood pressure and related quantities from the eight large‐scale population surveys carried out in South Africa between 1998 and 2015are not directly comparable, because of methodological differences and overall data quality. Second, structural equation modelling (and, within this general framework, multiple group modelling, normal‐censored regression, mixture analysis with skew‐normal distributions and the use of additional parameters and phantom variables) represent a viable and advantageous alternative to current methods of comparative analysis of blood pressure data. Conclusions: Encouraging signs regarding the future development of the burden of diseases related to elevated blood pressure in the South African population emerge from this study. Age‐specific prevalence of uncontrolled hypertension seems to be decreasing, especially among women, and this decrease is accompanied by declining mortality for cardiovascular disease, particularly for stroke, recorded in burden of mortality studies. The reasons of this decrease are largely unexplained and warrant further investigation. However, among the possible drivers analysed in this study, increased accessibility and efficacy of antihypertensive treatment are likely to be playing a role in the observed decrease in blood pressure. The growing obesity epidemic, on the contrary, is likely to be limiting the achievable benefits. Both of these factors can be targeted to maintain and improve the current decline in population values of blood pressure and prevalence of hypertension. The large seasonal variations of blood pressure and their unequal distribution across socioeconomic strata also suggest that interventions to reduce exposure to low temperatures might have public health benefit. From the point of view of the epidemiological investigation, the results of this study suggest that the current methods for the analysis of survey data on blood pressure and the measurement protocols for future data collections should be improved to increase between‐surveys comparabilityand gather more reliable information on temporal changes in BP and gain better understanding of their drivers. Specifically, analytical methods should take explicitly into account known sources of measurement and representation error to reduce their biasing effects, especially when inter‐survey comparisons are involved. Protocols for future studies should routinely include collection of auxiliary information and/or explicit validation of devices and procedures in the specific population

Analysing the socioeconomic determinants of hypertension in South Africa: a structural equation modelling approach

Abstract Background Epidemiological research has long observed a varying prevalence of hypertension across socioeconomic strata. However, patterns of association and underlying causal mechanisms are poorly understood in sub-Saharan Africa. Using education and income as indicators, we investigated the extent to which socioeconomic status is linked to blood pressure in the first wave of the National Income Dynamics Study — a South African longitudinal study of more than 15000 adults – and whether bio-behavioural risk factors mediate the association. Methods In a cross-sectional analysis, structural equation modelling was employed to estimate the effect of socioeconomic status on systolic and diastolic blood pressure and to assess the role of a set of bio-behavioural risk factors in explaining the observed relationships. Results After adjustment for age, race and antihypertensive treatment, higher education and income were independently associated with higher diastolic blood pressure in men. In women higher education predicted lower values of both diastolic and systolic blood pressure while higher income predicted lower systolic blood pressure. In both genders, body mass index was a strong mediator of an adverse indirect effect of socioeconomic status on blood pressure. Together with physical exercise, alcohol use, smoking and resting heart rate, body mass index therefore contributed substantially to mediation of the observed relationships in men. By contrast, in women unmeasured factors played a greater role. Conclusion In countries undergoing epidemiological transition, effects of socioeconomic status on blood pressure may vary by gender. In women, factors other than those listed above may have substantial role in mediating the association and merit investigation

Explaining population trends in cardiovascular risk: protocol for a comparative analysis of health transitions in South Africa and England using nationally representative survey data

Introduction Cardiovascular diseases (CVD) are the leading cause of death globally and share determinants with other major non-communicable diseases. Risk factors for CVD are routinely measured in population surveys and thus provide an opportunity to study health transitions. Understanding the drivers of health transitions in countries that have not followed expected paths compared with those that exemplified models of ‘epidemiologic transition’, such as England, can generate knowledge on where resources may best be directed to reduce the burden of disease. This study aims to examine the notions of epidemiological transition by identifying and quantifying the drivers of change in CVD risk in a middle-income African setting compared with a high-income European setting. Methods and analysis This is a secondary joint analysis of data collected within the scope of multiple population surveys conducted in South Africa and England between 1998 and 2017 on nationally representative samples of the adult population. The study will use a validated, non-laboratory risk score to estimate and compare the distribution of and trends in total CVD risk in the population. Statistical modelling techniques (fixed-effects and random-effects multilevel regression models and structural equation models) will be used to examine how various factors explain the variation in CVD risk over time in the two countries. Ethics and dissemination This study has obtained approval from the University of Greenwich (20.5.6.8) and Stellenbosch University (X21/09/027) Research Ethics Committees. It uses anonymised microdata originating from population surveys which received ethical approval from the relevant bodies, with no additional primary data collection. Results of the study will be disseminated through (1) peer-reviewed articles in open access journals; (2) policy briefs; (3) conferences and meetings; and (4) public engagement activities designed to reach health professionals, governmental bodies, civil society and the lay public. A harmonised data set will be made publicly available through online repositories

Multimorbidity patterns in South Africa: A latent class analysis

Introduction: South Africa has the largest burden of HIV worldwide and has a growing burden of non-communicable diseases; the combination of which may lead to diseases clustering in ways that are not seen in other regions. This study sought to identify common disease classes and sociodemographic and lifestyle factors associated with each disease class. Methods: Data were analyzed fromthe South AfricanDemographic andHealth Survey 2016. A latent class analysis (LCA) was conducted using nine disease conditions. Sociodemographic and behavioral factors associated with each disease cluster were explored. All analysis was conducted in Stata 15 and the LCA Stata plugin was used to conduct the latent class and regression analysis. Results: Multimorbid participants were included (n = 2 368). Four disease classes were identified: (1) HIV, Hypertension and Anemia (comprising 39.4% of the multimorbid population), (2) Anemia and Hypertension (23.7%), (3) Cardiovascular-related (19.9%) and (4) Diabetes and Hypertension (17.0%). Age, sex, and lifestyle risk factors were associated with class membership. In terms of age, with older adults were less likely to belong to the first class (HIV, Hypertension and Anemia). Males were more likely to belong to Class 2 (Anemia and Hypertension) and Class 4 (Diabetes and Hypertension). In terms of alcohol consumption, those that consumed alcohol were less likely to belong to Class 4 (Diabetes and Hypertension). Current smokers were more likely to belong to Class 3 (Cardiovascular-related). People with a higher body mass index tended to belong to Class 3 (Cardiovascular-related) or the Class 4 (Diabetes and Hypertension). Conclusion: This study a rmed that integrated care is urgently needed, evidenced by the largest disease class being an overlap of chronic infectious diseases and non-communicable diseases. This study also highlighted the need for hypertension to be addressed. Tackling the risk factors associated with hypertension could avert an epidemic of multimorbidity

Multimorbidity patterns in a national HIV survey of South African youth and adults

Information pertaining to multimorbidity is frequently informed by studies from high income countries and it is unclear how these findings relate to low and middle income countries, where the burden of infectious disease is high. South Africa has a quadruple burden of disease which includes a high HIV prevalence and a growing burden of non-communicable diseases. This study aimed to analyse the prevalence and patterns (disease classes or clusters) of multimorbidity in South Africa

Predictors of silicosis and variation in prevalence across mines among employed gold miners in South Africa

Background The stated intention to eliminate silicosis from the South African goldmining industry as well as current programmes to find and compensate ex-miners with silicosis require an understanding of variation in silicosis prevalence across the industry. We aimed to identify the predictors of radiological silicosis in a large sample of working miners across gold mines in South Africa. Methods Routine surveillance chest radiographs were collected from 15 goldmine “clusters” in a baseline survey undertaken in preparation for a separate tuberculosis isoniazid prophylaxis trial. All images were read for silicosis by a health professional experienced in using the International Labour Organisation (ILO) classification. Profusion thresholds of > 1/0 and > 1/1 were used. Demographic and occupational information was obtained by questionnaire. Predictors of silicosis were examined in a multivariable logistic regression model, including age, gender, racial ascription, country of origin, years since starting mine employment, mine shaft, skill category, underground work status and tuberculosis. Results The crude silicosis prevalence at ILO > 1/1 was 3.8% [95% confidence interval (CI) 3.5–4.1%]. The range across mine shafts was 0.8–6.9%. After adjustment for covariates, the interquartile range across shafts was reduced from 2.4 to 1.2%. Black miners [adjusted odds ratio (aOR) 2.8; 95% CI 1.1–7.2] and miners in full-time underground work (aOR 2.1; 95% CI 1.3–3.4) had substantially elevated odds of silicosis, while workers from Mozambique had lower odds (aOR 0.54; 95% CI 0.38–0.77). Silicosis odds rose sharply with both age and years since starting in the industry (p for linear trend  15 years since first exposure and 2.2% < 10 years. Conclusions In surveillance of silicosis in working gold miners time since first exposure remains a powerful predictor. Age appears to be an independent predictor, while the detection of radiological silicosis in short-service miners requires attention. Public risk reporting by mines should include factors bearing on silicosis prevalence, specifically dust concentrations, with independent verification. Studies of silicosis and tuberculosis in ex-miners are needed, supported by an accessible electronic database of the relevant medical and dust exposure records of all gold miners

Inequity in the distribution of non-communicable disease multimorbidity in adults in South Africa: An analysis of prevalence and patterns

The present study examined the prevalence and patterns of noncommunicable disease multimorbidity by wealth quintile among adults in South Africa. The South African National Income Dynamics Study Wave 5 was conducted in 2017 to examine the livelihoods of individuals and households. We analysed data in people aged 15 years and older (N = 27,042), including self-reported diagnosis of diabetes, stroke, heart disease and anthropometric measurements. Logistic regression and latent class analysis were used to analyse factors associated with multimorbidity and common disease patterns

Bayesian modelling of population trends in alcohol consumption provides empirically based country estimates for South Africa

Background Alcohol use has widespread effects on health and contributes to over 200 detrimental conditions. Although the pattern of heavy episodic drinking independently increases the risk for injuries and transmission of some infectious diseases, long-term average consumption is the fundamental predictor of risk for most conditions. Population surveys, which are the main source of data on alcohol exposure, suffer from bias and uncertainty. This article proposes a novel triangulation method to reduce bias by rescaling consumption estimates by sex and age to match country-level consumption from administrative data. Methods We used data from 17 population surveys to estimate age- and sex-specific trends in alcohol consumption in the adult population of South Africa between 1998 and 2016. Independently for each survey, we calculated sex- and age-specific estimates of the prevalence of drinkers and the distribution of individuals across consumption categories. We used these aggregated results, together with data on alcohol production, sales and import/export, as inputs of a Bayesian model and generated yearly estimates of the prevalence of drinkers in the population and the parameters that characterise the distribution of the average consumption among drinkers. Results Among males, the prevalence of drinkers decreased between 1998 and 2009, from 56.2% (95% CI 53.7%; 58.7%) to 50.6% (49.3%; 52.0%), and increased afterwards to 53.9% (51.5%; 56.2%) in 2016. The average consumption from 52.1 g/day (49.1; 55.6) in 1998 to 42.8 g/day (40.0; 45.7) in 2016. Among females the prevalence of current drinkers rose from 19.0% (17.2%; 20.8%) in 1998 to 20.0% (18.3%; 21.7%) in 2016 while average consumption decreased from 32.7 g/day (30.2; 35.0) to 26.4 g/day (23.8; 28.9). Conclusions The methodology provides a viable alternative to current approaches to reconcile survey estimates of individual alcohol consumption patterns with aggregate administrative data. It provides sex- and age-specific estimates of prevalence of drinkers and distribution of average daily consumption among drinkers in populations. Reliance on locally sourced data instead of global and regional trend estimates better reflects local nuances and is adaptable to the inclusion of additional data. This provides a powerful tool to monitor consumption, develop burden of disease estimates and inform and evaluate public health interventions

Course of perinatal depressive symptoms among South African women : associations with child outcomes at 18 and 36 months

CITATION: Garman, E. C., et al. 2019. Course of perinatal depressive symptoms among South African women : associations with child outcomes at 18 and 36 months. Social Psychiatry and Psychiatric Epidemiology, 54:1111-1123, doi:10.1007/s00127-019-01665-2.The original publication is available at https://link.springer.comENGLISH ABSTRACT: Purpose Latent modelling was used to identify trajectories of depressive symptoms among low-income perinatal women in South Africa. Predictors of trajectories and the association of trajectories with child outcomes were assessed. Methods This is a secondary analysis of data collected among women living in Cape Town settlements (N = 446). Participants were eligible if pregnant and 18 years or older, and included in the analysis if allocated to the control arm (routine perinatal care). Participants were excluded in case of non-singleton birth and baby death. Follow-up assessments were at 2 weeks, 6-, 18-, and 36-month postpartum. Trajectories of depressive symptoms were based on the Edinburgh Postnatal Depression Scale scores until 18-month postpartum, using latent class growth analysis. Child physical, cognitive, socioemotional, and behavioural outcomes were assessed at 18 and/or 36 months. Univariate and multivariate regressions were used to identify predictors of trajectories and differences in child outcomes. Results Four trajectories were identified: chronic low (71.1%), late postpartum (10.1%), early postpartum (14.4%), and chronic high (4.5%). Low social support, unwanted pregnancy, and risky drinking were associated with the chronic high trajectory; unemployment and HIV-positive status with the early postpartum trajectory; and intimate partner violence with the late postpartum trajectory. Weight-to-length and weight-for-age z-scores at 18 months, and weight-for-age z-scores, length-for-age z-scores, emotional symptom, and peer problem scores at 36 months differed across trajectories. Conclusions Severe depressive symptoms in postpartum period have a lasting effect on child physical and socio-emotional outcomes. Multiple screening throughout pregnancy and 1-year postpartum is essential.https://link.springer.com/article/10.1007%2Fs00127-019-01665-2https://link.springer.com/article/10.1007%2Fs00127-019-01665-2Publisher's versio