A systematic review of the association between pleural plaques and changes in lung function

Our plain-English summary of A systematic review of the association between pleural plaques and changes in lung function, by L. Kopylev, K.Y. Christensen, J.S. Brown, et al (Occupational and Environmental Medicine, 2015).

The study

• Authors: L. Kopylev, K.Y. Christensen, J.S. Brown, G.S. Cooper
• Journal: Occupational and Environmental Medicine
• Published: 2015;72(8):606-14
• Type of article: Systematic review
• Cited by: 29 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objectives: To conduct a systematic review of changes in lung function in relation to presence of pleural plaques in asbestos-exposed populations.

Methods: Database searches of PubMed and Web of Science were supplemented by review of papers' reference lists and journals' tables of contents. Methodological features (eg, consideration of potential confounding by smoking) of identified articles were reviewed by ≥ two reviewers. Meta-analyses of 20 studies estimated a summary effect of the decrements in per cent predicted (%pred) forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1) associated with presence of pleural plaques.

Results: Among asbestos-exposed workers, the presence of pleural plaques was associated with statistically significant decrements in FVC (4.09%pred, 95% CI 2.31 to 5.86) and FEV1 (1.99%pred, 95% CI 0.22 to 3.77). Effects of similar magnitude were seen when stratifying by imaging type (X-ray or high-resolution CT) and when excluding studies with potential methodological limitations. Undetected asbestosis was considered as an unlikely explanation of the observed decrements. Several studies provided evidence of an association between size of pleural plaques and degree of pulmonary decrease, and presence of pleural plaques and increased rate or degree of pulmonary impairment.

Conclusions: The presence of pleural plaques is associated with a small, but statistically significant mean difference in FVC and FEV1 in comparison to asbestos-exposed individuals without plaques or other abnormalities. From a public health perspective, small group mean decrements in lung function coupled with an increased rate of decline in lung function of the exposed population may be consequential.

Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

In plain English

This was a systematic review and meta-analysis of whether pleural plaques are linked to reduced lung function in asbestos-exposed people. A September 2013 database search yielded 30 studies; reference lists and journal contents added eight, totalling 38. The FVC analysis pooled 20 cross-sectional studies (15 chest X-ray, 5 high-resolution CT); the FEV1 analysis pooled 10 X-ray and 5 CT studies. Each compared exposed people with pleural plaques only against exposed people without plaques or other abnormalities; participants were generally male. Plaques were associated with lower forced vital capacity (FVC), by 4.09 percent of predicted (95% CI 2.31 to 5.86), and lower forced expiratory volume in one second (FEV1), by 1.99 percent of predicted (95% CI 0.22 to 3.77). Analysed separately, X-ray and CT studies each showed statistically significant FVC decrements but not statistically significant FEV1 decrements. Excluding studies with methodological limitations gave similar or larger decrements. The authors concluded that the difference was small but statistically significant, and that undetected parenchymal abnormalities were unlikely to fully account for it. They noted plaques might mark susceptibility rather than cause the decrease.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Systematic review and random-effects meta-analysis of published cross-sectional studies using internal comparison groups; longitudinal studies were reviewed separately
• Who was studied: 38 primary source studies. Screening of a PubMed and Web of Science search run on 25 September 2013 selected 30 studies. Eight more came from reference lists and from tables of contents of journals for papers released September to December 2013. The meta-analysis of FVC used 15 X-ray and 5 HRCT cross-sectional studies; the meta-analysis of FEV1 used 10 X-ray and 5 HRCT studies. The authors described the cross-sectional studies as studies of occupationally exposed workers from a variety of industries, generally male, with mean age at examination of about 50 to 60 years.
• Exposure: Asbestos exposure, mostly occupational. Of the included studies, 13 did not report fiber type, 4 reported mixed exposure, 2 reported mostly chrysotile exposure and 1 reported Libby tremolite (Libby amphibole asbestos) exposure.
• Main results:
  • In the pooled analyses (FVC: 15 X-ray and 5 HRCT studies; FEV1: 10 X-ray and 5 HRCT studies), asbestos-exposed people with pleural plaques had a change of -4.09 percent predicted FVC (95% CI -5.86 to -2.31) and -1.99 percent predicted FEV1 (95% CI -3.77 to -0.22) compared with exposed people without plaques. Both changes were statistically significant.
  • FVC analysed by imaging type: HRCT studies -3.30 percent predicted (95% CI -5.25 to -1.34) and X-ray studies -4.55 percent predicted (95% CI -6.73 to -2.38), both statistically significant.
  • FEV1 analysed by imaging type: HRCT studies -1.96 percent predicted (95% CI -6.01 to 2.09) and X-ray studies -1.87 percent predicted (95% CI -3.96 to 0.23), neither statistically significant. The authors attributed this to the smaller sample sizes.
  • In a sensitivity analysis excluding studies with methodological limitations, the FVC change was -4.08 percent predicted (95% CI -5.44 to -2.71; four studies) and the FEV1 change was -3.87 percent predicted (95% CI -5.84 to -1.90; three studies).
  • Because HRCT-only results were similar to X-ray results, the authors stated that undetected parenchymal abnormalities were unlikely to fully account for the lung function decrements.
  • Four cross-sectional studies examined the extent of plaques. The authors wrote that, taken together, these studies strongly suggest that greater plaque extent is associated with greater lung function decrease.
  • Four longitudinal studies had mean follow-up of 3.7 to 15 years. In the small study with about 15 years of follow-up of people with plaques only, there was a statistically significant decrease of 14.6 percent predicted FVC and 4.3 percent predicted FEV1 over the follow-up period.
• The authors' conclusion: The authors concluded that the presence of pleural plaques is associated with a small but statistically significant mean difference in FVC and FEV1 compared with asbestos-exposed individuals without plaques or other abnormalities. They also concluded that, from a public health perspective, such small group decrements together with an increased rate of decline may be consequential.
• Limitations the authors state:
  • Comparing exposed workers with and without plaques does not eliminate the possibility that workers with plaques had higher exposure.
  • People more sensitive to asbestos might develop both plaques and larger lung function decreases, so plaques may be a marker of susceptibility rather than the cause.
  • Smoking, body mass index and asbestos exposure were not measured in all studies.
  • Fiber characteristics could not be examined in the analysis.
  • Funnel plots for the HRCT analyses had few data points.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Pleural plaques and thickening.

Medical terms in this study, explained in our Lexicon: Systematic Review, Pleural Plaques, Confounding, FEV1, High-Resolution CT (HRCT).

Related studies

• Authors' response: A systematic review of the association between pleural plaques and changes in lung function — L. Kopylev, K.Y. Christensen, et al. (2015)
• Comment on "A systematic review of the association between pleural plaques and changes in lung function" by Kopylev et al (2014) — J.E. Goodman, L.E. Kerper, et al. (2015)
• Asbestos-induced pleural fibrosis and impaired lung function — D.A. Schwartz, L.J. Fuortes, et al. (1990)
• Risk and significance of chest radiograph and pulmonary function abnormalities in an elderly cohort of former nuclear weapons workers — M.A. Mikulski, P.G. Hartley, et al. (2011)
• Systematic review of pleural plaques and lung function — L.E. Kerper, H.N. Lynch, et al. (2015)
• Changes in lung function after surgery for mesothelioma — T. Ploenes, T. Osei-Agyemang, et al. (2013)

Browse more research in Occupational and Environmental Medicine, or return to medical research.