Kopylev et al 1 conducted a meta-analysis of lung function decrements associated with pleural plaques. Several factors indicate that this analysis was inappropriate.

Although Kopylev et al 1 considered study quality, they did not conduct a formal risk-of-bias analysis. Also, several studies did not provide data needed to calculate mean differences and SEs of lung function parameters. For these missing data, Kopylev et al 1 made assumptions and inputted values that may have biased results. Further, they excluded null studies that did not provide measurements without discussing how this likely impacted the interpretation of results. Most data in the meta-analysis were unadjusted for potential confounding by past asbestos exposure, smoking and body mass index. Kopylev et al 1 assumed that confounding factors were similar between comparison groups in each study, but several studies reported substantial differences between exposures and/or smoking (eg, Clin et al 2).

Kopylev et al 1 cited a longitudinal study3 showing lung function decrements over time in a population with pleural plaques. As this study had no comparison population, it is impossible to determine the cause of lung function loss. No other studies indicated longitudinal changes in lung function due to pleural plaques.

Finally, group mean lung function decrements were small (2–4%) and within normal intraindividual variation, indicating it was unlikely that pleural plaques caused clinically relevant changes in any individual.4

We conducted a systematic review of epidemiology studies5 that included 20 studies not cited by Kopylev et al,1 indicating their literature search strategy was insufficient. We found that the weight of evidence indicates that pleural plaques do not impact lung function, and any observed associations are likely due to undetected asbestos-related disease. The statistically significant meta-risk estimates reported by Kopylev et al 1 are likely a result of the primary studies’ methodological limitations, rather than an indication of causality.