Lung function and respiratory symptoms in subjects with asbestos-related disorders: a cross-sectional study

Our plain-English summary of Lung function and respiratory symptoms in subjects with asbestos-related disorders: a cross-sectional study, by B. Hilt, J.T. Lien, P.G. Lund-Larsen (American Journal of Industrial Medicine, 1987).

The study

• Authors: B. Hilt, J.T. Lien, P.G. Lund-Larsen
• Journal: American Journal of Industrial Medicine
• Published: 1987;11(5):517-28
• Cited by: 20 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. 000323).

Abstract

The prevalence of respiratory symptoms and lung function impairment was studied in a sample of men from a population screening of asbestos-related disorders. When the rates were adjusted for age and smoking habits, 83 subjects with lung fibrosis had an increased prevalence of respiratory symptoms, in particular, phlegm when coughing and breathlessness grades 1-3. Among 200 subjects under 70 years of age who had pleural plaques only, a statistically significant increase was observed in the prevalence of breathlessness grade 1 compared to an external reference population. Among 98 asbestos-exposed subjects who had normal chest X-rays, there was an increase in the prevalence of breathlessness grade 2, cough during the day, and phlegm when coughing. There was a higher proportion of subjects with lung fibrosis who were below 80% of the predicted values for forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) than in the other groups. There was also a higher proportion of subjects with pleural plaques only who were below 90% of the predicted value for FVC than in a group of 90 subjects without asbestos exposure. In accordance with previous studies, these results indicate that pleural plaques in asbestos workers may be of greater importance as a clinical feature than has been recognized in the past.

In plain English

This cross-sectional study examined breathing symptoms and lung function in men re-examined after an X-ray screening of men over 40 in Telemark, Norway. After exclusions for other lung diseases, 634 men were analysed: 83 with asbestos-related lung fibrosis (with or without pleural plaques), 363 with pleural plaques only, and 98 exposed and 90 unexposed men with normal X-rays. Symptoms, adjusted for age and smoking, were compared with 3,851 Oslo men. Among men under 70, grade 1 (mild) breathlessness was significantly more common in the fibrosis and plaques-only groups than in Oslo men. Exposed men with normal X-rays had more daytime cough and grade 2 breathlessness than unexposed men. A higher proportion of the fibrosis group than of any other group had forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) below 80% of predicted. Higher proportions of the fibrosis and plaques-only groups had FVC below 90% of predicted than of the unexposed group. The authors called their methods crude and differences small. They concluded the results might indicate pleural plaques are more clinically important than generally recognized.

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 study of men re-examined after a population X-ray and questionnaire screening, with internal and external comparison groups
• Who was studied: Men from a screening of 28,216 men over age 40 in Telemark county, Norway. Of the 1,372 who attended re-examination, 634 without other current lung disease were analysed: 83 with asbestos-related lung fibrosis (with or without pleural plaques), 363 with pleural plaques only, 98 exposed men with normal X-rays and 90 unexposed men with normal X-rays. Symptoms were also compared with a random sample of 3,851 Oslo men aged 40 to 70. Only study subjects aged 40 to 69 were used for that outside comparison. Study dates are not stated in the text.
• Exposure: Asbestos exposure, with no fiber type named. Exposure was graded as uncertain, light, moderate or heavy from each man's own account and the interviewer's knowledge of workplaces. Examples given were ship machine rooms, ferroalloy industries, automobile repair, building trades, industrial plumbers, maintenance workers, insulators, and use of asbestos jointing material or raw asbestos. Mean time from first exposure to diagnosis was 39.6 years for lung fibrosis and 37.3 years for pleural plaques.
• Main results:
  • Compared with the external Oslo reference population, breathlessness grade 1 was significantly more prevalent in the lung fibrosis group (group I) and the pleural plaques only group (group II). Breathlessness grade 2 was significantly more prevalent in the lung fibrosis group.
  • Phlegm when coughing was significantly more prevalent in the lung fibrosis group than in the pleural plaques only group (ages 40 to 69) and than in the unexposed normal X-ray group.
  • In exposed men with normal X-rays (group III), cough during the day was significantly more prevalent than in unexposed men (group IV) and than in the external reference population.
  • In exposed men with normal X-rays (group III), breathlessness grade 2 was significantly more prevalent than in unexposed men and than in the pleural plaques only group.
  • Apart from an excess of breathlessness grade 3 in the lung fibrosis group, the higher grades of breathlessness were more prevalent in the reference population than in the study population.
  • Lung function tended to be lower than predicted in groups I to III. Only forced vital capacity (FVC) in the lung fibrosis group was below the predicted value minus 2 standard deviations.
  • Significantly higher proportions of men in the lung fibrosis and pleural plaques only groups had FVC below 90% of predicted than unexposed men with normal X-rays.
  • A significantly higher proportion of the lung fibrosis group than of each of the other three groups had FVC and FEV1 below 80% of predicted.
  • Breathlessness grade 1 was related to the degree of asbestos exposure.
  • No clear relationship was found between breathlessness grade 1 and the duration of exposure.
• The authors' conclusion: The authors stated that, because the methods were crude and the differences small, the study does not give conclusive evidence about lung function disturbances in the different asbestos-related disorders. They concluded that men with lung fibrosis have more symptoms and lung function impairment than others. They added that the results might indicate pleural plaques in asbestos workers are more important clinically than generally recognized.
• Limitations the authors state:
  • The cross-sectional design may have involved uncontrolled selection. Men with asbestos injuries may have died before the study, and disability may have reduced participation. The authors said both could have led to underestimation.
  • Predicted lung function values came from a small reference group with a somewhat different age distribution. Spirometry was done standing in this study but sitting in the reference survey.
  • Many comparisons of respiratory symptoms were made, so some statistically significant results may have occurred by chance. The reference population also answered a mailed, slightly modified questionnaire.
  • Uncontrolled confounding was possible, for example from other lung diseases, unknown asbestos exposure in the reference population, other occupational exposures, social status and geographic differences.
  • No further lung function tests could be done, so small airway function could not be assessed.
  • The methods were crude and the observed differences small.

Topics

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

Medical terms in this study, explained in our Lexicon: Habit, Fibrosis, Pleural Plaques, Chest X-Ray, FEV1, Asbestos Exposure.

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• Decreased lung function in long-term asbestos cement workers: a cross-sectional study — C.G. Ohlson, T. Rydman, et al. (1984)
• Prevalence of anti-nuclear autoantibodies in subjects exposed to natural asbestiform fibers: a cross-sectional study — C. Ledda, R. Caltabiano, et al. (2018)
• Correlation between respiratory symptoms and pulmonary function in asbestos-exposed workers — C.A. Brodkin, S. Barnhart, et al. (1993)
• Longitudinal pattern of reported respiratory symptoms and accelerated ventilatory loss in asbestos-exposed workers — C.A. Brodkin, S. Barnhart, et al. (1996)

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