Sociodemographic, socioeconomic, clinical and behavioural predictors of body mass index vary by sex in rural South African adults-findings from the AWI-Gen study

ABSTRACT

Background: Despite increasing obesity in South African adults, data on the prevalence and determinants of body mass index (BMI) from rural communities, home to a significant proportion of the population, are scarce.

Objectives: To investigate overall and sex-specific determinants of BMI in a rural adult South African population undergoing rapid social and epidemiological transitions.

Methods: Baseline cross-sectional demographic, socioeconomic, anthropometric, clinical and behavioural data were collected between 2015 and 2016 from 1388 individuals aged 40–60 years and resident in the Agincourt sub-district of Mpumalanga province, a setting typical of rural northeast South Africa. A Health and Socio-Demographic Surveillance System (HDSS) underpins the sub-district and contributes to the Africa Wits-INDEPTH partnership for Genomic Studies (AWI-Gen). Linear regression was used to investigate univariate associations between log-transformed BMI and individual variables and multiple linear regression was used to investigate independent predictors of BMI overall and in sex-stratified analyses.

Results: Median BMI was significantly higher in females (28.7 kg/m²[95% CI 24.2–33.2] vs 23.0 kg/m²[95% CI 20.3–26.8];p < 0.001) with male sex associated with 17% lower BMI. In sex-stratified multiple linear regression models, compared to those never married, BMI was 7% higher in currently married males and 6% in currently married females. Current smoking in men and former smoking in women were associated with reductions in BMI of 13% and 26% respectively, compared with non-smokers. Higher educational attainment in women and higher socioeconomic status in men were both associated with higher BMI, while being HIV-positive and alcohol consumption in women were associated lower BMI.

Conclusions: Female sex strongly predicts higher BMI in this rural African population. While some predictors of higher BMI differ by sex, married individuals in both sexes had a higher BMI, suggesting that, in addition to developing sex-specific interventions to combat overweight and obesity, targeting married couples may result in reduction in population BMI.

KEYWORDS:

• Obesity
• gender
• South Africa
• BMI
• rural

Responsible Editor

Jennifer Stewart Williams, Umeå University, Sweden

Special Issue BMI distribution across African communities

Responsible Editor

Jennifer Stewart Williams, Umeå University, Sweden

Special Issue BMI distribution across African communities

Acknowledgments

The authors would like to acknowledge the study participants, fieldworkers and administrative staff and the contribution of Dr Sulaimon Afolabi to an earlier version of this manuscript. We would also like to acknowledge the support of the AWI-Gen secretariat, particularly Prof. Michèle Ramsay and Dr Stuart Ali.

Disclosure statement

No potential conflict of interest was reported by the authors.

Ethics and consent

Approval for this study was granted by the Human Research Ethics Committee (Medical) of the University of the Witwatersrand (M121029; M170880) and the Research and Ethics Committee of the Mpumalanga Province Department of Health

Paper context

Effective interventions are urgently needed to halt the increase in obesity in rural African populations, particularly given the scarcity of health resources to manage the consequent chronic non-communicable diseases. We demonstrate that while some predictors of higher body mass index in middle-aged and older adults in rural South Africa vary by sex, being married is a risk factor in both sexes and married couples may provide a target for public health interventions to reduce obesity.

Supplementary material

Supplementary data for this article can be accessed here.

Additional information

Funding

The AWI-Gen Collaborative Centre is funded by the National Human Genome Research Institute (NHGRI), Office of the Director (OD), the Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD), the National Institute of Environmental Health Sciences (NIEHS), the Office of AIDS Research (OAR) and the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), of the National Institutes of Health (NIH) under award number U54HG006938 and its supplements, as part of the H3Africa Consortium as well as by the Department of Science and Technology, South Africa, award number DST/CON 0056/2014, and by the African Partnership for Chronic Disease Research (APCDR).The Agincourt HDSS is supported by the Wellcome Trust, UK (058893/Z/99/A, 069683/Z/02/Z, 085477/Z/08/Z and 085477/B/08/Z), the University of the Witwatersrand and the South African Medical Research Council.Data for this study were collected in conjunction with Health and Ageing in Africa-a Longitudinal Study in an INDEPTH community (HAALSI). HAALSI is funded by the National Institute on Ageing (P01 AG041710) and is carried out through a collaboration between the Harvard Centre for Population and Development Studies at the Harvard T.H. Chan School of Public Health and the MRC/Wits Rural Public Health and Health Transitions Research Unit at the School of Public Health at the University of the Witwatersrand. Research reported in this publication was also supported by an NIH supplement (U54HG006938-03S1) awarded to the AWI-Gen Collaborative Centre (U54HG006938), to enable the integration of HAALSI and AWI-Gen research.AW is supported by the Fogarty International Centre of the National Institutes of Health under Award Number K43TW010698.This paper describes the views of the authors and does not necessarily represent the official views of the National Institutes of Health (USA), the South African Department of Science and Technology or the National Research Foundation (South Africa) who funded this research.

Notes on contributors

Ryan G. Wagner

RGW, NJC, FXGO, KK, ST and ANW contributed to the design of the study. RGW, MM and ZM contributed to the acquisition of the data. ANW and RGW contributed to the analysis and interpretation of data. RGW and ANW drafted the manuscript. All authors critically revised the manuscript and provided final approval of the version to be published. All authors agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.