Increased body mass index is related to apparent circumscribed pleural thickening on plain chest radiographs

Our plain-English summary of Increased body mass index is related to apparent circumscribed pleural thickening on plain chest radiographs, by Y.C. Lee, C.K. Runnion, S.C. Pang, et al (American Journal of Industrial Medicine, 2001).

The study

• Authors: Y.C. Lee, C.K. Runnion, S.C. Pang, N.H. de Klerk, A.W. Musk
• Journal: American Journal of Industrial Medicine
• Published: 2001;39(1):112-6
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Diffuse pleural thickening and pleural plaques are the commonest radiological manifestations of asbestos exposure. Differentiation between subpleural fat and non-calcified pleural plaques is important clinically and medico-legally. This study aims to determine if apparent circumscribed pleural thickening on chest radiographs is related with obesity.

Methods: Surveillance chest x-rays of 693 former asbestos workers were read with the ILO classification. Subjects with costophrenic angle obliteration (n = 57) were analyzed separately. The remaining subjects were subdivided according to their body mass index (BMI): Group 1 < 26 kg/m(2); Group 2 26-30 kg/m(2); Group 3 > 30 kg/m(2).

Results: Baseline characteristics, asbestos exposure, and profusion scores were evenly distributed. BMI of > 30 kg/m(2) was associated with a higher prevalence of pleural thickening on CXR (Gp1 = 8.5%; Gp2 = 9.3%; Gp3 = 18.3%). This relationship was strongest in the subgroups with 25-50% of the lateral chest wall involved and pleural thickness of < 10 mm.

Conclusions: Obesity (BMI > 30 kg/m(2)) is related to apparent circumscribed pleural thickening on CXR, especially thin (< 1 cm) shadows covering 25-50% of the lateral chest wall.

Copyright 2001 Wiley-Liss, Inc.

In plain English

This study asked whether body mass index (BMI, weight relative to height) was linked to apparent pleural thickening on ordinary chest x-rays. The subjects were former workers at the crocidolite mines in Wittenoom, Western Australia. Two readers scored the x-rays of 693 workers using the ILO classification, without knowing the workers' backgrounds. The 57 workers with costophrenic angle obliteration were analyzed separately. The remaining 636 were split into three BMI groups: under 26, 26 to 30, and over 30. Asbestos exposure scores and x-ray profusion scores were similar across the groups. On the right side of the chest, pleural thickening was seen in 8.5%, 9.3% and 18.3% of the three groups. Thin thickening (under 1 cm) covering 25 to 50% of the side chest wall on the right was seen in 13.4% of workers with BMI over 30, against 3.7% of those under 30. The authors concluded that obesity is related to apparent pleural thickening, probably at least partly because of fat. They said the study could not establish cause, which would require a CT study.

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: Cross-sectional analysis of surveillance chest x-rays (PA views) read by two readers using the ILO classification, compared across body mass index groups
• Who was studied: 693 former workers at the crocidolite mines in Wittenoom, Western Australia, who took part in a vitamin A program that included x-ray screening. 57 with costophrenic angle obliteration were analyzed separately. 636 (586 males) were in the main analysis: 164 with BMI under 26, 270 with BMI 26 to 30, and 202 with BMI over 30. Study dates are not given.
• Exposure: Crocidolite mining. Exposures were usually high, and median length of employment was 4 months. Cumulative exposure scores came from a previously validated model; mean cumulative crocidolite exposure was 20.2, 23.6 and 21.6 f/cc-years in the three BMI groups.
• Main results:
  • Among the 636 workers without costophrenic angle obliteration, pleural thickening in the right hemithorax was seen in 8.5% (BMI under 26), 9.3% (BMI 26 to 30) and 18.3% (BMI over 30). The corresponding left hemithorax figures were 9.1%, 8.9% and 14.4%.
  • Thickening covering 25 to 50% of the lateral chest wall and under 1 cm thick was seen in the right hemithorax of 27 of 202 workers (13.4%) with BMI over 30, against 16 of 434 (3.7%) with BMI under 30 (P less than 0.0001). In the left hemithorax the figures were 22 (10.9%) against 23 (5.3%), with a P value printed as 0.04. The authors described workers with BMI over 30 as about three times more likely to show such thickening.
  • Age, smoking, cumulative exposure and profusion scores were similar across the three BMI groups.
  • A subgroup analysis of the 50 female subjects showed a similar result.
  • Among the 57 workers with costophrenic angle obliteration, those with BMI over 30 were about twice as likely to have pleural thickening. The numbers were small and no significant differences were found between the subgroups of thickening.
  • In the first 100 cases, subcutaneous tissue thickness measured on the x-ray did not correlate with BMI or with pleural thickening.
• The authors' conclusion: The authors concluded that obesity, measured by BMI, is related to a higher prevalence of apparent pleural thickening on chest x-rays. They considered it probable that the effect is at least partly due to extrapleural fat, especially for thin shadows covering 25 to 50% of the chest wall.
• Limitations the authors state:
  • The study was not designed to establish a causal relationship; that would require a second-stage CT study.
  • The ILO scoring system does not describe where on the lateral chest wall the thickening lies.
  • Only standard PA x-rays were taken; oblique views, which may show pleural thickening better, were not used.
  • BMI may misclassify very muscular people as obese, and ideal BMI may differ between ethnic groups.
  • The subgroup with costophrenic angle obliteration was small.

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Wittenoom, Western Australia

All asbestos mines

Topics

Medical terms in this study, explained in our Lexicon: Pleural Thickening, Chest X-Ray, Diffuse Pleural Thickening, Pleural Plaques, Asbestos Exposure, ILO Classification, Costophrenic angle, Pleural Thickness.

Related studies

• Impact of body mass index on the detection of radiographic localized pleural thickening — T.C. Larson, A. Franzblau, et al. (2014)
• Diffuse thickening superimposed on circumscribed pleural thickening related to asbestos exposure — A. Miller, J.A. Miller (1993)
• Scoring CT/HRCT findings among asbestos-exposed workers: effects of patient's age, body mass index and common laboratory test results — T. Vehmas, L. Kivisaari, et al. (2005)
• Comparison of "B" readers' interpretations of chest radiographs for asbestos related changes — J.N. Gitlin, L.L. Cook, et al. (2004)
• 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 serratus anterior muscle on chest radiographs — D. Gilmartin (1979)

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