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. 2009 Aug;62(8):825-830.e10.
doi: 10.1016/j.jclinepi.2008.08.010. Epub 2009 Jan 10.

Updating meta-analyses leads to larger type I errors than publication bias

George F Borm  1 , A Rogier T Donders
Affiliations

Updating meta-analyses leads to larger type I errors than publication bias

George F Borm et al. J Clin Epidemiol. 2009 Aug.

Abstract

Objective: To estimate the extent to which the practice of periodically updating meta-analyses causes inflation of the type I error and then to compare the estimate with the inflation caused by publication bias. We also present a simple method to adjust for the inflation associated with updating meta-analyses.

Study design and setting: Simulations were used to estimate the error rates.

Results: In general, updating meta-analyses caused 2- to 5-fold inflation of the type I error rates, which exceeded the inflation caused by publication bias. As a rule of thumb, the results of a meta-analysis are robust up to 5, 10, 15, or 22 updates, if the P-value multiplied by 4, 6, 8, or 10 remains below the desired significance level.

Conclusion: Meta-analyses are likely to be updated until a clear conclusion is reached. Therefore, it is important to take the inflation of the error rate into account to interpret the results correctly.

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