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The Impact of Study Size on Meta-analyses: Examination of Underpowered Studies in Cochrane Reviews
BACKGROUND: Most meta-analyses include data from one or more small studies that, individually, do not have power to detect an intervention effect. The relative influence of adequately powered and underpowered studies in published meta-analyses has not previously been explored. We examine the distrib...
Autores principales: | , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
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Public Library of Science
2013
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3609745/ https://www.ncbi.nlm.nih.gov/pubmed/23544056 http://dx.doi.org/10.1371/journal.pone.0059202 |
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author | Turner, Rebecca M. Bird, Sheila M. Higgins, Julian P. T. |
author_facet | Turner, Rebecca M. Bird, Sheila M. Higgins, Julian P. T. |
author_sort | Turner, Rebecca M. |
collection | PubMed |
description | BACKGROUND: Most meta-analyses include data from one or more small studies that, individually, do not have power to detect an intervention effect. The relative influence of adequately powered and underpowered studies in published meta-analyses has not previously been explored. We examine the distribution of power available in studies within meta-analyses published in Cochrane reviews, and investigate the impact of underpowered studies on meta-analysis results. METHODS AND FINDINGS: For 14,886 meta-analyses of binary outcomes from 1,991 Cochrane reviews, we calculated power per study within each meta-analysis. We defined adequate power as ≥50% power to detect a 30% relative risk reduction. In a subset of 1,107 meta-analyses including 5 or more studies with at least two adequately powered and at least one underpowered, results were compared with and without underpowered studies. In 10,492 (70%) of 14,886 meta-analyses, all included studies were underpowered; only 2,588 (17%) included at least two adequately powered studies. 34% of the meta-analyses themselves were adequately powered. The median of summary relative risks was 0.75 across all meta-analyses (inter-quartile range 0.55 to 0.89). In the subset examined, odds ratios in underpowered studies were 15% lower (95% CI 11% to 18%, P<0.0001) than in adequately powered studies, in meta-analyses of controlled pharmacological trials; and 12% lower (95% CI 7% to 17%, P<0.0001) in meta-analyses of controlled non-pharmacological trials. The standard error of the intervention effect increased by a median of 11% (inter-quartile range −1% to 35%) when underpowered studies were omitted; and between-study heterogeneity tended to decrease. CONCLUSIONS: When at least two adequately powered studies are available in meta-analyses reported by Cochrane reviews, underpowered studies often contribute little information, and could be left out if a rapid review of the evidence is required. However, underpowered studies made up the entirety of the evidence in most Cochrane reviews. |
format | Online Article Text |
id | pubmed-3609745 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2013 |
publisher | Public Library of Science |
record_format | MEDLINE/PubMed |
spelling | pubmed-36097452013-03-29 The Impact of Study Size on Meta-analyses: Examination of Underpowered Studies in Cochrane Reviews Turner, Rebecca M. Bird, Sheila M. Higgins, Julian P. T. PLoS One Research Article BACKGROUND: Most meta-analyses include data from one or more small studies that, individually, do not have power to detect an intervention effect. The relative influence of adequately powered and underpowered studies in published meta-analyses has not previously been explored. We examine the distribution of power available in studies within meta-analyses published in Cochrane reviews, and investigate the impact of underpowered studies on meta-analysis results. METHODS AND FINDINGS: For 14,886 meta-analyses of binary outcomes from 1,991 Cochrane reviews, we calculated power per study within each meta-analysis. We defined adequate power as ≥50% power to detect a 30% relative risk reduction. In a subset of 1,107 meta-analyses including 5 or more studies with at least two adequately powered and at least one underpowered, results were compared with and without underpowered studies. In 10,492 (70%) of 14,886 meta-analyses, all included studies were underpowered; only 2,588 (17%) included at least two adequately powered studies. 34% of the meta-analyses themselves were adequately powered. The median of summary relative risks was 0.75 across all meta-analyses (inter-quartile range 0.55 to 0.89). In the subset examined, odds ratios in underpowered studies were 15% lower (95% CI 11% to 18%, P<0.0001) than in adequately powered studies, in meta-analyses of controlled pharmacological trials; and 12% lower (95% CI 7% to 17%, P<0.0001) in meta-analyses of controlled non-pharmacological trials. The standard error of the intervention effect increased by a median of 11% (inter-quartile range −1% to 35%) when underpowered studies were omitted; and between-study heterogeneity tended to decrease. CONCLUSIONS: When at least two adequately powered studies are available in meta-analyses reported by Cochrane reviews, underpowered studies often contribute little information, and could be left out if a rapid review of the evidence is required. However, underpowered studies made up the entirety of the evidence in most Cochrane reviews. Public Library of Science 2013-03-27 /pmc/articles/PMC3609745/ /pubmed/23544056 http://dx.doi.org/10.1371/journal.pone.0059202 Text en © 2013 Turner et al http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited. |
spellingShingle | Research Article Turner, Rebecca M. Bird, Sheila M. Higgins, Julian P. T. The Impact of Study Size on Meta-analyses: Examination of Underpowered Studies in Cochrane Reviews |
title | The Impact of Study Size on Meta-analyses: Examination of Underpowered Studies in Cochrane Reviews |
title_full | The Impact of Study Size on Meta-analyses: Examination of Underpowered Studies in Cochrane Reviews |
title_fullStr | The Impact of Study Size on Meta-analyses: Examination of Underpowered Studies in Cochrane Reviews |
title_full_unstemmed | The Impact of Study Size on Meta-analyses: Examination of Underpowered Studies in Cochrane Reviews |
title_short | The Impact of Study Size on Meta-analyses: Examination of Underpowered Studies in Cochrane Reviews |
title_sort | impact of study size on meta-analyses: examination of underpowered studies in cochrane reviews |
topic | Research Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3609745/ https://www.ncbi.nlm.nih.gov/pubmed/23544056 http://dx.doi.org/10.1371/journal.pone.0059202 |
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