Diffuse pleural thickening in asbestos workers: disability and lung function abnormalities

Our plain-English summary of Diffuse pleural thickening in asbestos workers: disability and lung function abnormalities, by C.R. McGavin, G. Sheers (Thorax, 1984).

The study

• Authors: C.R. McGavin, G. Sheers
• Journal: Thorax
• Published: 1984;39(8):604-7
• Cited by: 49 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000558).

Abstract

Data from 37 asbestos workers with diffuse pleural fibrosis have been analysed. None had radiological evidence of asbestosis or physiological evidence of airflow obstruction. Forty per cent had breathlessness of MRC grade 3 or higher. Vital capacity was significantly lower in the subjects in the higher grades of breathlessness and in those with greater radiographic pleural abnormality. No relationship was demonstrated between dust exposure and either radiographic abnormality or grade of breathlessness. Diffuse pleural thickening, particularly when extensive and bilateral, causes functional impairment and disability.

In plain English

This retrospective study examined records of 37 men exposed to asbestos at HM Dockyard, Devonport, who had diffuse pleural thickening. None had asbestos-related fibrosis of the lung tissue (parenchymal fibrosis) on X-ray, and none had airflow obstruction. Fifteen men (40%) reported breathlessness of grade 3 or higher, meaning they could not walk on level ground at a normal pace without breathlessness. Men in the higher breathlessness grades had significantly lower average FEV1 (77% versus 88% of predicted) and forced vital capacity (78% versus 87%). Men with the highest X-ray pleural scores (7 to 8) had average FEV1 and forced vital capacity of 72% and 71% of predicted. The figures were 90% and 88% for men with scores of 1 to 4. Higher X-ray scores were also associated with more breathlessness. Dust exposure ratings, known for 33 men, showed no relationship with X-ray score or breathlessness. The authors concluded that the results support the hypothesis that diffuse pleural fibrosis causes impaired lung function and disability. They noted that the study was retrospective, had no objective assessment of disability, and could not be certain that all the thickening was due to asbestos.

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: Retrospective analysis of medical records: chest X-rays, respiratory symptom questionnaires and lung function tests
• Who was studied: 37 men with diffuse pleural fibrosis, without asbestos-related parenchymal fibrosis or airflow obstruction, exposed to asbestos at HM Dockyard, Devonport. Most were identified in dockyard medical surveys and a few were referred to the Plymouth Chest Clinic. Mean age 54 years (SD 9).
• Exposure: Asbestos exposure at HM Dockyard, Devonport; the fiber type is not specified. For men with a detailed job history, an exposure rating was calculated as an estimated job exposure code multiplied by the years spent in that job.
• Main results:
  • 15 of the 37 men (40%) were in breathlessness grades 3, 4 and 5, meaning they claimed to be unable to walk on level ground at a normal pace without breathlessness.
  • The 8 men with pleural disease on one side had a mean breathlessness grade of 1.75. The 29 men with disease on both sides had a mean grade of 2.35.
  • Men in breathlessness grades 3 to 5 (n=15) had significantly lower mean FEV1 (77% of predicted) and FVC (78%) than men in grades 1 to 2 (n=22; 88% and 87%), p less than 0.05. The difference in total lung capacity was of borderline significance. When the 8 men with one-sided disease were excluded, statistical significance was no longer reached.
  • Higher radiographic pleural scores were significantly associated with greater breathlessness (p less than 0.025, chi-square test). Of the 15 men in grades 3 to 5, 8 had scores of 7 to 8. Of the 22 men in grades 1 to 2, 2 had scores of 7 to 8.
  • FEV1 and FVC declined significantly with increasing radiographic score. Mean FEV1 and FVC were 90% and 88% of predicted for scores 1 to 4 (n=15), 87% and 87% for scores 5 to 6 (n=12), and 72% and 71% for scores 7 to 8 (n=10). Excluding the men with one-sided disease did not affect the reduction in the highest-score group.
  • Transfer coefficient (Kco) rose from a mean of 92% for radiographic scores 1 to 3, to 114% for scores 4 to 6 and 112% for scores 7 and 8 (p less than 0.025).
  • The dust exposure rating was known for 33 of the 37 men. It showed no relationship with either radiographic score or breathlessness grade.
• The authors' conclusion: The authors concluded that the results support the hypothesis that diffuse pleural fibrosis is a cause of impaired lung function and of disability, whether or not other asbestos-related disease is present.
• Limitations the authors state:
  • The study was a retrospective analysis of data collected mainly in dockyard surveys, with no objective assessment of disability.
  • It was not certain that the pleural thickening was due to asbestos in every case, particularly in the 8 men with one-sided disease.
  • Lung tissue fibrosis may have contributed to disability and lung function abnormality. It can be present without showing on X-ray, and pleural fibrosis makes the X-ray assessment harder.
  • Few men had severe disability. Very disabled men may have left the dockyard, or men with extensive disease on both sides may have been excluded because readers could not rule out lung opacities.

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: Diffuse Pleural Thickening, Fibrosis, Obstructive Lung Disease, Bilateral.

Related studies

• Asbestos-related lesions of the pleura: parietal plaques compared to diffuse thickening studied with chest roentgenography, computed tomography, lung function, and gas exchange — G. Hillerdal, P. Malmberg, 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)
• The presentation and natural history of asbestos-induced diffuse pleural thickening — V. Jeebun, S.C. Stenton (2012)
• Asbestos-related pleural diseases: dimensional criteria are not appropriate to differentiate diffuse pleural thickening from pleural plaques — J. Ameille, M. Matrat, et al. (2004)
• Asbestos-related diffuse pleural thickening — N. Fujimoto, K. Kato, et al. (2014)
• A retrospective study on radiological findings of diffuse pleural thickening with benign asbestos pleural effusion in Japanese cases — T. Kishimoto, K. Kato, et al. (2022)

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