Review of Mustafic et al.'s Main air pollutants and myocardial infarction: a systematic review and meta-analysis. JAMA. 307:713-721

Evaluation of a meta-analysis of air quality and heart attacks, a case study. S. Stanley Young and Warren B. Kindzierski. Critical Review in Toxicology, Jan 2019. https://doi.org/10.1080/10408444.2019.1576587

ABSTRACT: It is generally acknowledged that claims from observational studies often fail to replicate. An exploratory study was undertaken to assess the reliability of base studies used in meta-analysis of short-term air quality-myocardial infarction risk and to judge the reliability of statistical evidence from meta-analysis that uses data from observational studies. A highly cited meta-analysis paper examining whether short-term air quality exposure triggers myocardial infarction was evaluated as a case study. The paper considered six air quality components - carbon monoxide, nitrogen dioxide, sulphur dioxide, particulate matter 10um and 2.5um in diameter (PM10 and PM2.5), and ozone. The number of possible questions and statistical models at issue in each of 34 base papers used were estimated and p-value plots foreach of the air components were constructed to evaluate the effect heterogeneity of p-values used from the base papers. Analysis search spaces (number of statistical tests possible) in the base paperswere large, median=12,288 (interquartile range = 2496 — 58,368), in comparison to actual statistical test results presented. Statistical test results taken from the base papers may not provide unbiased measures of effect for meta-analysis. Shapes of p-value plots for the six air components were consistent with the possibility of analysis manipulation to obtain small p-values in several base papers. Results suggest the appearance of heterogeneous, researcher-generated p-values used in the meta-analysis rather than unbiased evidence of real effects for air quality. We conclude that this meta-analysis does not provide reliable evidence for an association of air quality components with myocardial risk.

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As of April 2018 theWeb of Science indicated that this study had received enough citations to place it in the top 1% of the academic field of Clinical Medicine for the publication year 2012.