Cited by 295Meta-analysis and systematic reviewsAnimal testing and alternativesAcademic integrity and plagiarism

Evaluation of excess significance bias in animal studies of neurological diseases

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Tsilidis, Konstantinos K., Panagiotou, Orestis A., Sena, Emily S., Aretouli, Eleni, Evangelou, Evangelos, Howells, David W., Salman, Rustam Al-Shahi, Macleod, Malcolm R. +1 more·2013·PLoS Biology

Abstract

Animal studies generate valuable hypotheses that lead to the conduct of preventive or therapeutic clinical trials. We assessed whether there is evidence for excess statistical significance in results of animal studies on neurological disorders, suggesting biases. We used data from meta-analyses of interventions deposited in Collaborative Approach to Meta-Analysis and Review of Animal Data in Experimental Studies (CAMARADES). The number of observed studies with statistically significant results (O) was compared with the expected number (E), based on the statistical power of each study under different assumptions for the plausible effect size. We assessed 4,445 datasets synthesized in 160 meta-analyses on Alzheimer disease (n = 2), experimental autoimmune encephalomyelitis (n = 34), focal ischemia (n = 16), intracerebral hemorrhage (n = 61), Parkinson disease (n = 45), and spinal cord injury (n = 2). 112 meta-analyses (70%) found nominally (p≤0.05) statistically significant summary fixed effects. Assuming the effect size in the most precise study to be a plausible effect, 919 out of 4,445 nominally significant results were expected versus 1,719 observed (p<10⁻⁹). Excess significance was present across all neurological disorders, in all subgroups defined by methodological characteristics, and also according to alternative plausible effects. Asymmetry tests also showed evidence of small-study effects in 74 (46%) meta-analyses. Significantly effective interventions with more than 500 animals, and no hints of bias were seen in eight (5%) meta-analyses. Overall, there are too many animal studies with statistically significant results in the literature of neurological disorders. This observation suggests strong biases, with selective analysis and outcome reporting biases being plausible explanations, and provides novel evidence on how these biases might influence the whole research domain of neurological animal literature.

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  • Analysing the data using different methods and selectively reporting those with statistically significant results constitutes p-hacking and introduces bias in the literature.

    “Analysing the data using different methods and selectively reporting those with statistically significant results constitutes p-hacking and introduces bias in the literature [90,94].”
  • Failure to disclose all the outcomes that were measured introduces bias in the literature, as positive outcomes are reported more often.

    “Failure to disclose all the outcomes that were measured introduces bias in the literature, as positive outcomes (e.g., those statistically significant) are reported more often [88–91].”

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Research works printed but not linked: 2

  1. [45]Sena ES, van der Worp HB, Bath PM, Howells DW, Macleod MR (2010) Publication bias in reports of animal stroke studies leads to major overstatement of efficacy. PLoS Biol 8: e1000344 doi: 10.1371/journal.pbio.1000344 20361022 PMC2846857 · DOI · Paper page
  2. [47]Higgins J, Green S, editors (2008) Cochrane Handbook for Systematic Reviews of Interventions. Chichester, England: The Cochrane Collaboration and John Wiley & Sons Ltd.

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Authors
Tsilidis, K. K., Panagiotou, O. A., Sena, E. S., Aretouli, E., Evangelou, E., Howells, D. W., Salman, R. A.-S., Macleod, M. R., & Ioannidis, J. P. A.
Affiliations
  • University of Ioannina (GR)
  • The University of Melbourne (AU)
  • Universidad de Deusto (ES)
  • University of Edinburgh (GB)
  • Stanford Medicine (US)
Corresponding author
Ioannidis, John P. A.
Venue
PLoS Biology
Published
2013-07-16
Volume
11
Issue
7
Pages
e1001609
ISSN
  • 1544-9173 (ISSN-L)
  • 1545-7885
OpenAlex
W2136462620
Cited by
295
References
50
Citations by year
2026: 8 · 2025: 16 · 2024: 14 · 2023: 25 · 2022: 13 · 2021: 19 · 2020: 21 · 2019: 25 · 2018: 19 · 2017: 27 · 2016: 31 · 2015: 31 · 2014: 36 · 2013: 10
FWCI
39.72
Type
journal article
Language
en
Open access
Locations
  • PLoS Biology (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Minerva Access (University of Melbourne) (submittedVersion, cc-by)
  • eCite Digital Repository (University of Tasmania) (submittedVersion)
  • RePEc: Research Papers in Economics (submittedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • Figshare (submittedVersion, cc-by)
  • Edinburgh Research Explorer (University of Edinburgh) (submittedVersion, cc-by)
  • Spiral (Imperial College London) (submittedVersion, other-oa)
Funders
  • National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC/K000659/1, NC/L000970/1)
  • Medical Research Council
Topics
  • Social Sciences › Decision Sciences › Statistics, Probability and Uncertainty › Meta-analysis and systematic reviews
  • Health Sciences › Veterinary › Small Animals › Animal testing and alternatives
  • Social Sciences › Safety Research › Academic integrity and plagiarism
Keywords
animal studies, neurological disorders, statistical power, selective reporting, small-study effects, Alzheimer's disease, experimental autoimmune encephalomyelitis, focal cerebral ischemia, intracerebral hemorrhage, Parkinson's disease, spinal cord injury
MeSH terms
Animals, Disease Models, Animal, Nervous System Diseases, Research Design, Bias

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