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Magnitude of effects in clinical trials published in high-impact general medical journals

Konstantinos C M Siontis1, Evangelos Evangelou, John P A Ioannidis

  • 1Clinical Trials and Evidence-Based Medicine Unit, Department of Hygiene and Epidemiology, University of Ioannina School of Medicine, Ioannina, Greece.

International Journal of Epidemiology
|November 1, 2011
PubMed

Insights

High-impact journals publish more favorable results for small experimental intervention trials, especially early ones. Large trials show no difference in effect sizes regardless of journal prestige.

Area of Science:

  • Medical research publication bias
  • Clinical trial reporting standards
  • Scientific journal impact

Background:

  • Prestigious journals prioritize important and informative studies.
  • Investigated potential bias in high-impact general (HIG) medical journals regarding experimental intervention results.

Purpose of the Study:

  • To determine if HIG journals systematically publish more favorable results for experimental interventions compared to other literature.
  • To analyze the influence of trial size and publication timing on reported effect sizes in HIG journals.

Main Methods:

  • Systematic review of Cochrane Database and meta-analyses from four general journals (2008-09).
  • Included meta-analyses with ≥1 binary outcome and ≥1 clinical trial.
  • Compared effect sizes from trials in NEJM, JAMA, or Lancet with those in other journals using summary relative odds ratios (sRORs).

Main Results:

  • Analyzed 79 meta-analyses comprising 1043 trials.
  • Trials in HIG journals showed similar effects to others for large-scale evidence.
  • Small trials (<40 events) in HIG journals had more favorable results (sROR 1.64).
  • Early small trials in HIG journals showed the most prominent effect inflation (sROR 2.68).

Conclusions:

  • Small trials in prestigious journals report more favorable experimental intervention effects.
  • This effect inflation is most pronounced in early-published trials within high-impact journals.
  • No significant effect inflation was observed for large trials.
Abstract

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