What contributions do languages other than English make on the results of meta-analyses?

J Clin Epidemiol. 2000 Sep;53(9):964-72. doi: 10.1016/s0895-4356(00)00188-8.


Including only a portion of all available evidence may introduce systematic errors into the meta-analytic process and threaten its validity. We set out to examine whether language restricted meta-analyses, compared to language inclusive meta-analyses, provide different estimates of the effectiveness of interventions evaluated in randomized trials. We identified and retrieved all 79 meta-analyses from several disease areas in which explicit eligibility criteria regarding trial selection were reported. General characteristics and quality of reporting of the meta-analyses were assessed using a validated instrument. We explored the effects of language of publication of the randomized trials on the quantitative results using logistic regression analyses. Language restricted meta-analyses, compared to language inclusive meta-analyses, did not differ with respect to the estimate of benefit of the effectiveness of an intervention (ROR = 0.98; 95% CI: 0.81-1.17). These results were also robust after a series of sensitivity analyses. This study provides no evidence that language restricted meta-analyses lead to biased estimates of intervention effectiveness. We encourage others to replicate this study using different sampling frames, clinical topics and interventions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Humans
  • Language*
  • Logistic Models
  • Meta-Analysis as Topic*
  • Outcome Assessment, Health Care*
  • Randomized Controlled Trials as Topic
  • Selection Bias*