Income and obesity: what is the direction of the relationship? A systematic review and meta-analysis

ObjectiveIt was repeatedly shown that lower income is associated with higher risks for subsequent obesity. However, the perspective of a potential reverse causality is often neglected, in which obesity is considered a cause for lower income, when obese people drift into lower-income jobs due to labo...

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Bibliographic Details
Published in:BMJ open Vol. 8; no. 1; p. e019862
Main Authors: Kim, Tae Jun, von dem Knesebeck, Olaf
Format: Journal Article
Language:English
Published: England BMJ Publishing Group LTD 01.01.2018
BMJ Publishing Group
Subjects:
Adults
Body mass index
Causality
Child development
Education
Educational attainment
Evidence-based medicine
Family income
Health care
Health Knowledge, Attitudes, Practice
Humans
Income - statistics & numerical data
Influence
Meta-analysis
Obesity
Obesity - economics
Obesity - etiology
Pediatrics
Prospective Studies
Public Health
Qualitative Research
Risk Factors
Social Environment
Social isolation
Socioeconomic Factors
Sociology
Stereotypes
Stigma
Systematic review
Wages & salaries
United Kingdom > UK
causation
reverse causality
obesity
Income
ISSN:2044-6055, 2044-6055
Online Access:Get full text
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Summary:ObjectiveIt was repeatedly shown that lower income is associated with higher risks for subsequent obesity. However, the perspective of a potential reverse causality is often neglected, in which obesity is considered a cause for lower income, when obese people drift into lower-income jobs due to labour–market discrimination and public stigmatisation. This review was performed to explore the direction of the relation between income and obesity by specifically assessing the importance of social causation and reverse causality.DesignSystematic review and meta-analysis.MethodsA systematic literature search was conducted in January 2017. The databases Medline, PsycINFO, Sociological Abstracts, International Bibliography of Social Sciences and Sociological Index were screened to identify prospective cohort studies with quantitative data on the relation between income and obesity. Meta-analytic methods were applied using random-effect models, and the quality of studies assessed with the Newcastle-Ottawa Scale.ResultsIn total, 21 studies were eligible for meta-analysis. All included studies originated from either the USA (n=16), the UK (n=3) or Canada (n=2). From these, 14 studies on causation and 7 studies on reverse causality were found. Meta-analyses revealed that lower income is associated with subsequent obesity (OR 1.27, 95% CI 1.10 to 1.47; risk ratio 1.52, 95% CI 1.08 to 2.13), though the statistical significance vanished once adjusted for publication bias. Studies on reverse causality indicated a more consistent relation between obesity and subsequent income, even after taking publication bias into account (standardised mean difference −0.15, 95% CI −0.30 to 0.01). Sensitivity analyses implied that the association is influenced by obesity measurement, gender, length of observation and study quality.ConclusionsFindings suggest that there is more consistent evidence for reverse causality. Therefore, there is a need to examine reverse causality processes in more detail to understand the relation between income and obesity.PROSPERO registration number 42016041296.
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ISSN:2044-6055
2044-6055
DOI:10.1136/bmjopen-2017-019862