The relation among pulmonary function, chest roentgenographic abnormalities, and smoking status in an asbestos-exposed cohort

Our plain-English summary of The relation among pulmonary function, chest roentgenographic abnormalities, and smoking status in an asbestos-exposed cohort, by L. Rosenstock, S. Barnhart, N.J. Heyer, et al (The American Review of Respiratory Disease, 1988).

The study

• Authors: L. Rosenstock, S. Barnhart, N.J. Heyer, D.J. Pierson, L.D. Hudson
• Journal: The American Review of Respiratory Disease
• Published: 1988;138(2):272-7
• Cited by: 94 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. 000269).

Abstract

To clarify the clinical value of the International Labor Office (ILO) roentgenographic classification of pneumoconiosis in assessing asbestos-exposed persons, we determined the relationships among spirometric values, radiographic evidence of parenchymal pulmonary fibrosis and/or pleural thickening, and cigarette smoking history in 684 consecutively enrolled male plumbers and pipefitters participating in a larger cross-sectional prevalence study. The subjects were mainly marine pipefitters (35%), plumbers (24%), and steamfitters/welders (23%); 28% had never smoked, 39% were ex-smokers, and 33% currently smoked cigarettes. Mean values for FVC and FEV1 were 95.0 and 91.9% of predicted, respectively, with mean FEV1/FVC ratio 77.7%; by standard criteria, 7.8% had restrictive impairment, and 21.7%, obstructive defects. Chest radiographs were normal in 63% and showed pleural abnormalities only in 17%, parenchymal abnormalities only in 7%, and both pleural and parenchymal abnormalities in 12%. Both FVC and FEV1 correlated with the degree of small opacity profusion, as assessed by ILO grade. Pleural abnormalities were associated with lower FVC values, independently of ILO profusion grade for Grades less than or equal to 1/0, and were unexplained by smoking status. In addition, there was a positive association between smoking history and degree of ILO parenchymal abnormality, particularly in those with the heaviest cumulative smoking history. Our results suggest that the ILO classification of pneumoconiosis, although a useful epidemiologic tool, should be applied with caution in persons with asbestos exposure, and that pleural abnormalities may be associated with physiologic impairment in such persons.

In plain English

This cross-sectional study examined 681 male plumbers and pipefitters in a 1982-1984 union surveillance program in Seattle and Tacoma. Exposure was measured as years in the trade; the article does not identify the cohort's fiber types. On chest X-rays graded by the International Labor Office (ILO) system, 63% were normal, 17% had pleural abnormalities only, 7% parenchymal (lung tissue) only, and 12% both. Lung function (FVC) fell progressively as ILO profusion grade rose. Restrictive impairment affected 12% at grade 1/0, 17% at 1/1 and 30% at 1/2. Pleural thickening was associated with lower mean FVC. Within age groups, ever and never smokers did not differ significantly in X-ray pleural or parenchymal abnormalities. In an age-adjusted logistic regression, men with 45 or more pack-years had an odds ratio of 2.75 (p less than 0.01) for X-ray parenchymal fibrosis. The authors concluded that the ILO classification should be applied clinically with caution and that pleural abnormalities may contribute to impairment, though they could not tell whether the pleural changes themselves or lung fibrosis invisible on X-ray was responsible. They noted low participation limits generalization.

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 prevalence study
• Who was studied: 681 male plumbers and pipefitters, drawn from the first 700 participants enrolled 1982 to 1984 in a voluntary surveillance program for Seattle Local 32 and Tacoma-based Local 82 (16 women and 3 men with incomplete records were excluded)
• Exposure: Work in the plumbing and pipefitting trades (marine pipefitters, plumbers, steamfitters and welders, refrigeration and others), with exposure measured as years in the trade. Mean duration was 17.1 years. The article does not identify the asbestos fiber types this cohort encountered.
• Main results:
  • Of the 681 chest X-rays, 63% showed no abnormality, 17% pleural abnormalities only, 7% parenchymal abnormalities only, and 12% both
  • 7.8% of the men (53) had restrictive impairment and 21.7% (148) had obstructive defects
  • Mean percent predicted FVC declined progressively with increasing ILO profusion grade (F = 7.9, p less than 0.001)
  • Isolated restrictive impairment affected 12% of men with ILO grade 1/0 X-rays, 17% with 1/1 and 30% with 1/2
  • Men with pleural thickening had a lower mean percent predicted FVC than men without pleural abnormalities (97% versus 89%), regardless of whether parenchymal fibrosis was also present
  • Bilateral diffuse pleural thickening, present in 63 men (9%), was associated with lower percent predicted FVC than no pleural disease in each ILO grade. The difference was statistically significant in categories 0/- or 0/0 and 1/0.
  • Among men with minimal interstitial fibrosis (ILO 1/0), isolated bilateral plaques were associated with a significantly lower percent predicted FVC
  • Within 10-year age strata, there were no significant differences between ever and never smokers in the prevalence of X-ray parenchymal (ILO 1/0 or greater) or pleural abnormalities
  • Level of smoking did not significantly affect the risk of pleural abnormalities
  • In a logistic regression using dummy variables for age and smoking strata, the highest smoking category (45 or more pack-years) had an odds ratio of 2.75 (p less than 0.01) for X-ray parenchymal fibrosis. No other smoking category showed an effect approaching significance.
  • The largest mean difference between heavy smokers and never smokers was less than one minor category of the 12-point ILO profusion scale
• The authors' conclusion: The authors concluded that the ILO classification, although a useful epidemiologic tool, should be applied with caution in the clinical evaluation of asbestos-exposed persons. They also concluded that even discrete pleural abnormalities may contribute to impairment, whether or not they reflect interstitial fibrosis that is not apparent on X-ray. They could not determine which of these explains the effect.
• Limitations the authors state:
  • Low participation rates limit the ability to generalize about how common these abnormalities are in the whole eligible population
  • The data could not show whether the effect of pleural abnormalities on lung function came from the pleural changes themselves or from accompanying lung-tissue fibrosis. Only biopsy could address this.
  • The authors could not determine whether heavy smoking enhances the X-ray appearance of asbestos-induced fibrosis or increases small opacity profusion by other means

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis.

Medical terms in this study, explained in our Lexicon: Pneumoconiosis, Pulmonary Fibrosis, Pleural Thickening, Pipefitter, FEV1, FEV1/FVC Ratio, Chest X-Ray, ILO Classification.

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