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  • Body composition and physical activity as mediators in the relationship between socioeconomic status and blood pressure in young South African women: a structural equation model analysis

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Epidemiology
Research
Body composition and physical activity as mediators in the relationship between socioeconomic status and blood pressure in young South African women: a structural equation model analysis
  1. Richard J Munthali1,
  2. Mercy Manyema1,2,
  3. Rihlat Said-Mohamed1,
  4. Juliana Kagura1,3,
  5. Stephen Tollman4,5,6,
  6. Kathleen Kahn4,5,6,
  7. F Xavier Gómez-Olivé4,
  8. Lisa K Micklesfield1,
  9. David Dunger1,7,
  10. Shane A Norris1
  1. 1 MRC/Wits Developmental Pathways for Health Research Unit, Department of Paediatrics, School of Clinical Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
  2. 2 DST-NRF Centre of Excellence in Human Development, University of the Witwatersrand, Johannesburg, South Africa
  3. 3 Division of Epidemiology and Biostatistics, School of Public Health, University of the Witwatersrand, Johannesburg, South Africa.
  4. 4 MRC/Wits Rural Public Health and Health Transitions Research Unit, School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
  5. 5 INDEPTH Network, Accra, Ghana
  6. 6 Umeå Centre for Global Health Research, Umeå, Sweden
  7. 7 Department of Paediatrics, MRL Wellcome Trust-MRC Institute of Metabolic Science, NIHR Cambridge Comprehensive Biomedical Research Centre, University of Cambridge, Cambridge, UK
  1. Correspondence to Dr Richard J Munthali; munthali{at}aims.ac.za

Abstract

Objectives Varying hypertension prevalence across different socioeconomic strata within a population has been well reported. However, the causal factors and pathways across different settings are less clear, especially in sub-Saharan Africa. Therefore, this study aimed to compare blood pressure (BP) levels and investigate the extent to which socioeconomic status (SES) is associated with BP, in rural and urban South Africa women.

Setting Rural and urban South Africa.

Design Cross-sectional.

Participants Cross-sectional data on SES, total moderate and vigorous physical activity (MVPA), anthropometric and BP were collected on rural (n=509) and urban (n=510) young black women (18–23 years age). Pregnant and mentally or physically disabled women were excluded from the study.

Results The prevalence of combined overweight and obesity (46.5% vs 38.8%) and elevated BP (27.0% vs 9.3%) was higher in urban than rural women, respectively. Results from the structural equation modelling showed significant direct positive effects of body mass index (BMI) on systolic BP (SBP) in rural, urban and pooled datasets. Negative direct effects of SES on SBP and positive total effects of SES on SBP were observed in the rural and pooled datasets, respectively. In rural young women, SES had direct positive effects on BMI and was negatively associated with MVPA in urban and pooled analyses. BMI mediated the positive total effects association between SES and SBP in pooled analyses (ß 0.46; 95% CI 0.15 to 0.76).

Conclusions Though South Africa is undergoing nutritional and epidemiological transitions, the prevalence of elevated BP still varies between rural and urban young women. The association between SES and SBP varies considerably in economically diverse populations with BMI being the most significant mediator. There is a need to tailor prevention strategies to take into account optimising BMI when designing strategies to reduce future risk of hypertension in young women.

  • hypertension
  • obesity
  • socioeconomic status
  • physical activity
  • structural equation model
  • body mass index

This is an open access article distributed in accordance with the Creative Commons Attribution 4.0 Unported (CC BY 4.0) license, which permits others to copy, redistribute, remix, transform and build upon this work for any purpose, provided the original work is properly cited, a link to the licence is given, and indication of whether changes were made. See: https://creativecommons.org/licenses/by/4.0/.

http://dx.doi.org/10.1136/bmjopen-2018-023404

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    Footnotes

    • Contributors RJM and SAN conceptualised the manuscript. RJM analysed the data. RJM, MM, RS-M, JK, ST, KK, FXG-O, LKM, DD and SAN interpreted the data. RJM wrote the manuscript and all authors were involved in editing and approving the final manuscript.

    • Funding SAN is supported by the UK MRC DfID African Research Leader Scheme and by the DST-NRF Centre of Excellence in Human Development at the University of the Witwatersrand, Johannesburg. Birth to Twenty data collection was supported by the Wellcome Trust under grant (092097/Z/10/Z). The MRC/Wits- Agincourt Unit is supported by the South African Medical Research Council, and the Wellcome Trust under grants (058893/Z/99/A, 069683/Z/02/Z, 085477/Z/08/Z, 085477/B/08/Z).

    • Disclaimer Opinions expressed and conclusions arrived at are those of the authors and are not to be attributed to the CoE in Human Development.

    • Competing interests None declared.

    • Patient consent Not required.

    • Ethics approval The study protocols were approved by the Human Research Ethics Committee of the University of the Witwatersrand (Clearance certificates M120138 for the Ntshembo-Hope Cross-Sectional Survey in Agincourt and M111182 for the BT20 + survey).

    • Provenance and peer review Not commissioned; externally peer reviewed.

    • Data sharing statement The datasets used and/or analysed during the current study are available from the Developmental Pathways for Health Research Unit data management department by contacting SAN on reasonable request.

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    © Author(s) (or their employer(s)) 2018. Re-use permitted under CC BY. Published by BMJ. This is an open access article distributed in accordance with the Creative Commons Attribution 4.0 Unported (CC BY 4.0) license, which permits others to copy, redistribute, remix, transform and build upon this work for any purpose, provided the original work is properly cited, a link to the licence is given, and indication of whether changes were made. See: https://creativecommons.org/licenses/by/4.0/.