Changing patterns in asbestos-induced lung disease

Our plain-English summary of Changing patterns in asbestos-induced lung disease, by J. Ohar, D.A. Sterling, E. Bleecker, et al (Chest, 2004).

The study

• Authors: J. Ohar, D.A. Sterling, E. Bleecker, J. Donohue
• Journal: Chest
• Published: 2004;125(2):744-53
• Cited by: 49 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Study Objectives: To determine patterns in asbestos-induced lung diseases found in older, less exposed workers.

Design: Review of a database evaluating lung function, smoking status, form of asbestos-induced lung disease, and radiograph abnormalities.

Setting: Outpatient clinic.

Participants: A total of 3383 asbestos-exposed workers referred for independent medical evaluation, including control subjects who lacked asbestos-specific radiograph abnormalities (n = 243), subjects with low International Labor Organization (ILO) scores (n = 2,685), high ILO scores (n = 312), bronchogenic cancer (n = 63), and mesothelioma (n = 80). Of these, 3,327 workers have specific smoking status information and 3,312 workers have lung volume measures.

Interventions: Chest radiographs were interpreted by a certified B-reader, and abnormalities were quantified according to the ILO scoring system. Spirometry and lung volume measurement were performed. Subjects completed a self-administered questionnaire that was reviewed at the time of examination. Control subjects were screened on two separate occasions at least 10 years apart to exclude subclinical or slowly progressive asbestos-induced lung disease.

Measurements And Results: The mean age of the population was 65.1 +/- 9.9 years, and the latency was 41.4 +/- 10.1 years (+/- SD). Most subjects (41.8%) had normal pulmonary function. Obstruction was the most common pulmonary function abnormality (25.4%), followed by restriction (19.3%) and a mixed pattern (6.0%). Most subjects (79.4%) had low ILO scores. Benign pleural abnormalities were the only findings in 54% of subjects with low ILO score. Subjects with high ILO scores were older, smoked more, and had a longer latency than subjects with low ILO scores and control subjects. Smokers were younger, had a shorter latency, and had paradoxically greater ILO scores than nonsmokers. Subjects with bronchogenic cancer and mesothelioma had longer latencies than control subjects and subjects with benign asbestos-induced lung disease.

Conclusions: Asbestos-induced lung disease today is characterized by low ILO scores, long latencies, greater disease magnitude in smokers, and a normal or obstructive pattern of pulmonary function abnormality. Spirometric evaluation in the absence of lung volume measurements caused misclassification that resulted in overestimation of the presence of a restrictive pattern of pulmonary function.

In plain English

This was a review of a registry of 3,383 asbestos-exposed workers, recruited from legal cases, who were referred for independent medical evaluation. Workers had chest X-rays scored on the International Labor Organization (ILO) scale, questionnaires and, except a small percentage (mainly those with advanced lung cancer or mesothelioma), breathing tests. Mean age was 65.1 years; mean time since first exposure was 41.4 years. Most workers (79.4%) had low ILO scores. In 54% of these, pleural abnormalities were the only finding. Overall, 41.8% had normal lung function; obstruction (25.4%) outnumbered restriction (19.3%). High-score workers were older, smoked more and had longer latency than low-score workers and controls. Current smokers were younger and had shorter latency than former smokers and nonsmokers, and had higher ILO scores than nonsmokers. Workers with mesothelioma or bronchogenic cancer had longer latency than control subjects and low-score workers. Spirometry without lung volume measurements overestimated restriction. The authors concluded that asbestos-induced lung disease today features low ILO scores, long latencies, greater disease in smokers, and normal or obstructive lung function. They acknowledged possible selection bias.

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: Descriptive review of a registry database of asbestos-exposed workers seen in an outpatient clinic, with cross-sectional comparisons by disease group and smoking status
• Who was studied: 3,383 asbestos-exposed workers in the Selikoff registry who were referred for independent medical evaluation. Referrals came from trade unions and from television and newspaper advertisements.

The groups were:

• 243 control subjects with no asbestos-related X-ray abnormality, screened twice at least 10 years apart
• 2,685 with low ILO scores
• 312 with high ILO scores
• 63 with bronchogenic cancer
• 80 with mesothelioma

Mean age was 65.1 years (range 28 to 93); 96% were male and 93% white. The exact location and dates of evaluation are not stated.

• Exposure: Documented workplace asbestos exposure, with at least 10 years since first exposure; mean latency was 41.4 years. Fiber types are not specified. Trades are shown only in a figure that is not in the text. Smoking was also studied, both as current, former or never smoking and in pack-years.
• Main results:
  • A small percentage of subjects could not undergo pulmonary function testing, primarily those with advanced lung cancer or mesothelioma.
  • In the whole population, 41.8% had normal lung function. Obstruction was the most common abnormality (25.4%), followed by restriction (19.3%) and a mixed pattern (6.0%).
  • 79.4% of subjects had low ILO scores. In 54% of subjects with low ILO scores, benign pleural abnormalities were the only finding.
  • Subjects with high ILO scores were older, smoked more and had longer latency than subjects with low ILO scores and control subjects. Mean latency was 45.8 years in the high-score group, 40.5 years in the low-score group and 39.8 years in controls.
  • Current smokers were significantly younger and had shorter latency than former smokers and nonsmokers. Mean age was 60.3 years for current smokers, 66.3 for former smokers and 64.9 for nonsmokers. Mean latency was 37.2, 42.8 and 41.2 years respectively. Current smokers also had a significantly greater numeric ILO score than nonsmokers (2.2 vs 1.8).
  • Subjects with mesothelioma (mean latency 46.5 years) and bronchogenic cancer (45.8 years) had longer latency than control subjects and subjects with low ILO scores, but not longer than subjects with high ILO scores.
  • Spirometry alone found a purely restrictive pattern in 23.8% of the population. Spirometry without lung volume measurements overestimated restriction and underestimated obstruction. Among subjects with obstruction and a reduced FVC, hyperinflation explained the reduced FVC in 83% of smokers and 71% of nonsmokers.
  • With lung volumes measured, obstruction was the most common abnormality in the low ILO, high ILO and bronchogenic cancer groups. In the mesothelioma group, restriction was the most common. Restriction was more common with high ILO scores (25.0%) than with low ILO scores (17.8%).
  • Control subjects had low frequencies of obstruction (11.8%) and restriction (11.8%).
• The authors' conclusion: The authors concluded that asbestos-induced lung disease today is characterized by low ILO scores, long latencies, greater disease magnitude in smokers, and a normal or obstructive pattern of lung function. They also concluded that spirometry without lung volume measurements overestimated restriction.
• Limitations the authors state:
  • The authors acknowledged that recruiting subjects from legal cases based on an abnormal X-ray could raise a question of selection bias. They argued that the study was controlled by using coworkers as control subjects, and that fewer than 1% of potential subjects declined to take part.
  • The authors stated that the study is descriptive.

Topics

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

Medical terms in this study, explained in our Lexicon: Bronchogenic Carcinoma, Mesothelioma, Chest X-Ray, B-Reader, Spirometry, Latency, Obstructive Lung Disease.

Related studies

• Changing patterns in asbestos-induced lung disease — P. De Vuyst, P.A. Gevenois, et al. (2004)
• Chronic obstructive lung diseases and risk of non-small cell lung cancer in women — A.G. Schwartz, M.L. Cote, et al. (2009)
• Asbestos-induced and smoking-related disease: apportioning pulmonary function deficit by using thin-section CT — S.J. Copley, Y.C. Lee, et al. (2007)
• Changing patterns of lung cancer in the United States — W.J. Blot, J.F. Fraumeni (1982)
• Changing clinical course of patients with malignant mesothelioma: implications for FNA cytology and utility of immunocytochemical staining — G.H. Yu, L. Soma, et al. (2001)
• Incidence of mesothelioma in Lombardy, Italy: exposure to asbestos, time patterns and future projections — C. Mensi, S. De Matteis, et al. (2016)

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