Use of relative and absolute effect measures in reporting health inequalities: structured review
BMJ 2012; 345 doi: https://doi.org/10.1136/bmj.e5774 (Published 03 September 2012) Cite this as: BMJ 2012;345:e5774
- Nicholas B King, assistant professor1,
- Sam Harper, assistant professor2,
- Meredith E Young, assistant professor3
- 1Biomedical Ethics Unit, McGill University Faculty of Medicine, 3647 Peel St, Montreal, QC, Canada H3A 1X1
- 2Department of Epidemiology, Biostatistics and Occupational Health, McGill University Faculty of Medicine, Montreal H3A 1A2
- 3Department of Medicine, McGill University Faculty of Medicine, Montreal H3A 1A1
- Correspondence to: N B King nicholas.king{at}mcgill.ca
- Accepted 13 August 2012
Abstract
Objective To examine the frequency of reporting of absolute and relative effect measures in health inequalities research.
Design Structured review of selected general medical and public health journals.
Data sources 344 articles published during 2009 in American Journal of Epidemiology, American Journal of Public Health, BMJ, Epidemiology, International Journal of Epidemiology, JAMA, Journal of Epidemiology and Community Health, The Lancet, The New England Journal of Medicine, and Social Science and Medicine.
Main outcome measures Frequency and proportion of studies reporting absolute effect measures, relative effect measures, or both in abstract and full text; availability of absolute risks in studies reporting only relative effect measures.
Results 40% (138/344) of articles reported a measure of effect in the abstract; among these, 88% (122/138) reported only a relative measure, 9% (13/138) reported only an absolute measure, and 2% (3/138) reported both. 75% (258/344) of all articles reported only relative measures in the full text; among these, 46% (119/258) contained no information on absolute baseline risks that would facilitate calculation of absolute effect measures. 18% (61/344) of all articles reported only absolute measures in the full text, and 7% (25/344) reported both absolute and relative measures. These results were consistent across journals, exposures, and outcomes.
Conclusions Health inequalities are most commonly reported using only relative measures of effect, which may influence readers’ judgments of the magnitude, direction, significance, and implications of reported health inequalities.
Footnotes
We thank Jessica Adam-Smith, Phongsack Manivong, Luke Mondor, and Amy Styles for valuable research assistance.
Contributors: All authors contributed to the conception, critical review, study design, and data interpretation. SH did the analysis. NBK produced the first draft. All authors approved the final version. NBK is the guarantor.
Funding: This work was supported by Canadian Institutes of Health Research Operating Grant No 107530.
Competing interests: All authors have completed the Unified Competing Interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.
Ethical approval: Not needed.
Data sharing: Dataset and statistical code available from corresponding author at nicholas.king{at}mcgill.ca.
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