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The Impact of Study Size on Meta-analyses: Examination of Underpowered Studies in Cochrane Reviews

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  • Rebecca M Turner
  • Sheila M Bird
  • Julian P T Higgins

Abstract

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

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  • Rebecca M Turner & Sheila M Bird & Julian P T Higgins, 2013. "The Impact of Study Size on Meta-analyses: Examination of Underpowered Studies in Cochrane Reviews," PLOS ONE, Public Library of Science, vol. 8(3), pages 1-8, March.
    • Handle: RePEc:plo:pone00:0059202
    DOI: 10.1371/journal.pone.0059202
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    References listed on IDEAS

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    1. Gordon H Guyatt & Edward J Mills & Diana Elbourne, 2008. "In the Era of Systematic Reviews, Does the Size of an Individual Trial Still Matter?," PLOS Medicine, Public Library of Science, vol. 5(1), pages 1-3, January.
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    Cited by:

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    2. Sarah Fischer & Shannon Hyder & Arlene Walker, 2020. "The effect of employee affective and cognitive trust in leadership on organisational citizenship behaviour and organisational commitment: Meta-analytic findings and implications for trust research," Australian Journal of Management, Australian School of Business, vol. 45(4), pages 662-679, November.
    3. Christian Gunge Riberholt & Vibeke Wagner & Jane Lindschou & Christian Gluud & Jesper Mehlsen & Kirsten Møller, 2020. "Early head-up mobilisation versus standard care for patients with severe acquired brain injury: A systematic review with meta-analysis and Trial Sequential Analysis," PLOS ONE, Public Library of Science, vol. 15(8), pages 1-33, August.
    4. Catherine J. Carter-Snell & D. Gaye Warthe, 2023. "“Stepping Up”: A Decade of Relationship Violence Prevention," Social Sciences, MDPI, vol. 12(9), pages 1-15, September.
    5. Vibeke Koushede & Carina Sjöberg Brixval & Lau Caspar Thygesen & Solveig Forberg Axelsen & Per Winkel & Jane Lindschou & Christian Gluud & Pernille Due, 2017. "Antenatal small-class education versus auditorium-based lectures to promote positive transitioning to parenthood – A randomised trial," PLOS ONE, Public Library of Science, vol. 12(5), pages 1-17, May.
    6. Rennert, Lindiwe, 2022. "A meta-analysis of the impact of rail stations on property values: Applying a transit planning lens," Transportation Research Part A: Policy and Practice, Elsevier, vol. 163(C), pages 165-180.
    7. Seetha Anitha & David Ian Givens & Rosemary Botha & Joanna Kane-Potaka & Nur Liana Binti Sulaiman & Takuji W. Tsusaka & Kowsalya Subramaniam & Ananthan Rajendran & Devraj J. Parasannanavar & Raj Kumar, 2021. "Calcium from Finger Millet—A Systematic Review and Meta-Analysis on Calcium Retention, Bone Resorption, and In Vitro Bioavailability," Sustainability, MDPI, vol. 13(16), pages 1-14, August.
    8. Navin Kumar & Kamila Janmohamed & Kate Nyhan & Laura Forastiere & Wei Hong Zhang & Anna Kågesten & Maximiliane Uhlich & Sarah S.M. Van de Velde & Joel J.M. Francis & Jennifer Toller Erausquin & Elin E, 2021. "Sexual health and COVID-19: protocol for a scoping review," ULB Institutional Repository 2013/320377, ULB -- Universite Libre de Bruxelles.

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