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International Journal for Equity in Health
Published in: International Journal for Equity in Health 1/2018

Open Access 01-12-2018 | Research

Income inequality and cardiovascular disease risk factors in a highly unequal country: a fixed-effects analysis from South Africa

Authors: Kafui Adjaye-Gbewonyo, Ichiro Kawachi, S. V. Subramanian, Mauricio Avendano

Published in: International Journal for Equity in Health | Issue 1/2018

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Abstract

Background

Chronic stress associated with high income inequality has been hypothesized to increase CVD risk and other adverse health outcomes. However, most evidence comes from high-income countries, and there is limited evidence on the link between income inequality and biomarkers of chronic stress and risk for CVD. This study examines how changes in income inequality over recent years relate to changes in CVD risk factors in South Africa, home to some of the highest levels of income inequality globally.

Methods

We linked longitudinal data from 9356 individuals interviewed in the 2008 and 2012 National Income Dynamics Study to district-level Gini coefficients estimated from census and survey data. We investigated whether subnational district income inequality was associated with several modifiable risk factors for cardiovascular disease (CVD) in South Africa, including body mass index (BMI), waist circumference, blood pressure, physical inactivity, smoking, and high alcohol consumption. We ran individual fixed-effects models to examine the association between changes in income inequality and changes in CVD risk factors over time. Linear models were used for continuous metabolic outcomes while conditional Poisson models were used to estimate risk ratios for dichotomous behavioral outcomes.

Results

Both income inequality and prevalence of most CVD risk factors increased over the period of study. In longitudinal fixed-effects models, changes in district Gini coefficients were not significantly associated with changes in CVD risk factors.

Conclusions

Our findings do not support the hypothesis that subnational district income inequality is associated with CVD risk factors within the high-inequality setting of South Africa.
Appendix
Available only for authorised users
Footnotes
1
Plausible readings were considered as 50 mmHg ≤ SBP ≤ 250 mmHg, 30 mmHg ≤ DBP ≤ 150 mmHg, and mean SBP > mean DBP [48, 84].
 
2
Waist circumference measurements greater than 190.5 cm (75 in.) or less than 50.8 cm (20 in.) [85] were considered implausible.
 
3
Household incomes of zero were given an income of one so that the log would return a value of 0.
 
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Metadata
Title
Income inequality and cardiovascular disease risk factors in a highly unequal country: a fixed-effects analysis from South Africa
Authors
Kafui Adjaye-Gbewonyo
Ichiro Kawachi
S. V. Subramanian
Mauricio Avendano
Publication date
01-12-2018
Publisher
BioMed Central
Published in
International Journal for Equity in Health / Issue 1/2018
Electronic ISSN: 1475-9276
DOI
https://doi.org/10.1186/s12939-018-0741-0

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