Influence of Socioeconomic Status and Body Composition on Blood Pressure in South African Young Adults: The Birth to Twenty Cohort Open Access

Abstract

Objective:

We assessed relationships between composite measures of socioeconomic status (SES) and blood pressure measures in South African young adults, and investigated the potential moderating or mediating role of body mass index (BMI).

Participants and Setting:

Participants of the Young Adult Survey of Birth to Twenty (Bt20), an urban longitudinal birth cohort from Soweto, Johannesburg, South Africa.

Methods:

Multivariate linear and logistic regression models were used to explore the influence of socioeconomic indices on two measures of the outcome of blood pressure: continuous systolic blood pressure (SBP) and the dichotomous presence of hypertension or pre-hypertension. Models controlled for height, body mass index (BMI), and potential interaction between BMI and SES. Mediation analyses were conducted using effect decomposition and assessment of potential mediation by BMI on the direct and indirect effects of SES on SBP.

Results:

Pre-hypertension prevalence was 39.8% in males and 25.8% in females, and hypertension prevalence was 7.9% in males and 5.7% in females. Caregiver's highest grade at the time of the participant's birth and internet access in males, and wealth quintile at birth, being married or cohabitating, completion of grade 12, MNet/satellite access, and internet access in females were independently associated with measures of blood pressure in bivariate analysis. However composite measures of SES showed associations with systolic blood pressure and pre-hypertension / hypertension only after consideration of interaction between SES and BMI, and a high percentage of the effect of SES on blood pressure was mediated by obesity when effect-mediator interaction was present.

Conclusions:

BMI appeared to have a stronger influence on young adult SBP and pre-hypertension / hypertension than all measures of SES, but significant moderation and mediation was observed between BMI and various measures of SES. Further research is needed into the role of BMI as a mediator or moderator on SES and young adult blood pressure, and to investigate whether individual components of SES may predict young adult blood pressure.

Table of Contents

Chapter I: Literature Review...............................................................................................1

Chapter II: Manuscript......................................................................................................15

Abstract...........................................................................................................................15

Introduction.....................................................................................................................16

Methods...........................................................................................................................18

Results.............................................................................................................................26

Discussion........................................................................................................................31

Chapter III: Summary, Future Directions, & Public Health Implications................................36

Tables and Figures.............................................................................................................37

References........................................................................................................................50

About this Master's Thesis

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School	Rollins School of Public Health
Department	Epidemiology
Degree	MSPH
Submission	Master's Thesis
Language	English
Research Field	Health Sciences, Public Health Health Sciences, General Health Sciences, Epidemiology
Keyword	socioeconomic status South Africa young adult hypertension blood pressure obesity
Committee Chair / Thesis Advisor	Stein, Aryeh D, Emory University
Partnering Agencies	International Non-governmental organization (e.g., CARE, Inc.) University, college or educational institution (other than Emory)

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