Asbestos-related pleural plaques and lung function

Our plain-English summary of Asbestos-related pleural plaques and lung function, by L.C. Oliver, E.A. Eisen, R. Greene, et al (American Journal of Industrial Medicine, 1988).

The study

• Authors: L.C. Oliver, E.A. Eisen, R. Greene, N.L. Sprince
• Journal: American Journal of Industrial Medicine
• Published: 1988;14(6):649-56
• Cited by: 59 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000257).

Abstract

The present study examines the association between asbestos-related pleural plaques and lung function in a group of workers with occupational exposure to asbestos. Exposure, smoking, and respiratory histories, chest radiographs, flow-volume loops, and single breath DLCOs were obtained on 383 railroad workers. A score based on the ILO-1980 classification system was used to quantify the extent of plaquelike thickening. In order to eliminate potential confounders, we excluded from final analysis subjects with diffuse pleural thickening (n = 10) or small irregular opacities classified as profusion 0/1 or greater (n = 6) on chest radiograph. Definite pleural plaques were observed in 22.6%. The single breath DLCO was similar in the groups with and without plaques (p = 0.0550). Decrement in FVC and the occurrence of pulmonary restriction were associated with the presence of definite plaques (p = 0.0306 and 0.0431, respectively) and with quantitative pleural score (p = 0.0135 and 0.0126), controlling for duration of asbestos exposure and smoking. A test for trend revealed an association between level of diagnostic certainty (none, suspect, definite) for pleural plaques and these measures of lung function (p less than 0.02). Our findings reveal an association between asbestos-related pleural plaques and decrement in lung function as measured by FVC and criteria for pulmonary restriction.

In plain English

This cross-sectional study of 383 central Pennsylvania railroad yard workers examined whether asbestos-related pleural plaques on chest X-rays were linked to reduced lung function. Of 377 white men, the authors excluded those with diffuse pleural thickening or X-ray signs of lung scarring, and two with unreadable films, leaving 359. Asbestos levels were unmeasured; years employed stood in for exposure. Definite plaques were found in 22.6% (81 men). Accounting for exposure duration and smoking, plaques were associated with a 4.3 percentage-point lower forced vital capacity (FVC, percent of predicted) and with a restrictive breathing pattern. Restriction affected 18% of men with plaques versus 9% without. Diffusing capacity was lower with plaques in absolute terms but not significantly as percent of predicted; it was lower in the 14 men with both plaques and restriction than in those with neither. Shortness of breath was more common with plaques, but not after adjustment. The authors concluded that their findings suggest an independent association between plaques and reduced lung function. They called the FVC loss's clinical significance uncertain and could not rule out hidden lung scarring.

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 morbidity study
• Who was studied: 383 railroad workers from a central Pennsylvania railroad yard. Data analysis was carried out on 377 white males. The authors excluded 6 with small opacities (possible interstitial fibrosis), 10 with diffuse pleural thickening and 2 with unreadable chest radiographs, which left 359. The article does not give study dates.
• Exposure: Occupational asbestos exposure in railroad work. The article does not specify the fiber type. Measured asbestos dust levels were not available, so duration of employment was used as a stand-in for exposure.
• Main results:
  • Definite pleural plaques were seen in 22.6% (81) of the 359 workers analyzed.
  • Controlling for exposure and smoking, pleural plaques were significantly associated with FVC, percent of predicted (p = 0.0306).
  • The presence of plaques was associated with a decrement of 4.3 percentage points for FVC.
  • In logistic regression accounting for asbestos exposure and smoking, pleural plaques were associated with pulmonary restriction (p = 0.0431) but not with obstruction (p = 0.8860).
  • Restriction was found in 18% (15) of the group with plaques, compared with 9% (25) of the group without plaques (X2 = 5.75, p = 0.017).
  • The quantitative pleural score and the grade of plaque by diagnostic certainty were positively associated with restriction (p = 0.0126 and 0.0250, respectively).
  • Absolute values of FVC, FEV1 and single breath DLCO (diffusing capacity) were significantly lower in the group with plaques than in the group without.
  • When expressed as percent predicted, which takes age and height into account, the difference between groups remained significant for FVC and FEV1 but not for single breath DLCO (p = 0.0550).
  • Mean single breath DLCO, percent predicted, was 88.4 in the group with both plaques and restriction (n = 14), compared with 101.4 in the group with neither (n = 250).
  • In univariate analysis, dyspnea (shortness of breath) was more common in the group with plaques: 39.5% vs. 26.6% (p = 0.025).
  • After multivariate control for asbestos exposure and smoking, the authors observed no correlation between dyspnea and pleural plaques, pleural score, or extent of plaques.
• The authors' conclusion: The authors concluded that their findings suggest an independent association between asbestos-related pleural plaques and decrement in lung function. They suggested that having both plaques and restriction may be a marker of interstitial fibrosis that does not show on X-ray.
• Limitations the authors state:
  • The authors could not exclude with certainty asbestos-induced interstitial fibrosis as a confounder.
  • Without airborne asbestos measurements, asbestos exposure may not have been adequately controlled in the analysis.
  • The clinical significance of the 4.3 percentage-point FVC decrement is uncertain.

Topics

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

Medical terms in this study, explained in our Lexicon: Pleural Plaques, Occupational Exposure, Chest X-Ray, Diffusing Capacity (DLCO), Diffuse Pleural Thickening, Asbestos Exposure.

Related studies

• Railroad workers with pleural plaques: I. Spirometric and nitrogen washout investigation on smoking and nonsmoking asbestos-exposed workers — U. Hjortsberg, P. Orbaek, et al. (1988)
• Railroad workers with pleural plaques: II. Small airway dysfunction among asbestos-exposed workers — U. Hjortsberg, P. Orbaek, et al. (1988)
• Asbestos-related disease in railroad workers. A cross-sectional study — L.C. Oliver, E.A. Eisen, et al. (1985)
• Railways and asbestos in Japan (1928-1987)--epidemiology of pleural plaques, malignancies and pneumoconioses- — Y. Hosoda, Y. Hiraga, et al. (2008)
• Do asbestos-related pleural plaques on HRCT scans cause restrictive impairment in the absence of pulmonary fibrosis? — B. Clin, C. Paris, et al. (2011)
• A systematic review of the association between pleural plaques and changes in lung function — L. Kopylev, K.Y. Christensen, et al. (2015)

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