Lung function and exercise performance in smoking and nonsmoking asbestos-exposed workers

Our plain-English summary of Lung function and exercise performance in smoking and nonsmoking asbestos-exposed workers, by D.Y. Sue, A. Oren, J.E. Hansen, et al (The American Review of Respiratory Disease, 1985).

The study

• Authors: D.Y. Sue, A. Oren, J.E. Hansen, K. Wasserman
• Journal: The American Review of Respiratory Disease
• Published: 1985;132(3):612-8
• Cited by: 32 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. 000513).

Abstract

Evaluation of impairment caused by exposure to an occupational toxin can be complicated by additional exposure to other injurious agents. Because cigarette smoking is common and cigarettes are implicated in obstructive lung disease and cardiovascular diseases, we assessed the contribution of smoking to functional abnormalities in a group of asbestos-exposed shipyard workers. Seventy-three workers who never smoked were paired with 73 current smokers by age and asbestos exposure. Pulmonary function and performance during cycle incremental exercise were compared between the 2 groups. Nonsmokers had significantly higher VC, FEV1, FEV1/VC, and diffusing capacity for carbon monoxide than did smokers. Only 3 of the 73 nonsmokers but 23 of the 73 smokers had a FEV1/VC below the 95% confidence limit of predicted value. The FEF25-75%, on the other hand, failed to identify additional subjects with obstruction not found by the FEV1/VC. During exercise, despite no difference in maximal heart rate, the maximal O2 uptake (VO2max) and oxygen-pulse were lower among smokers. In addition, smokers more frequently had abnormal AaPO2 at maximal exercise. Of 33 smokers who had a VO2max less than 80% of predicted, 16 were judged to have cardiac disease, whereas only 2 appeared to be limited by obstruction. Only 15 of the 73 nonsmokers had a VO2max less than 80%. We conclude that cigarette smoking was the major contributing factor to the obstructive lung disease observed in asbestos workers, and it also had a strong influence on the occurrence, nature, and magnitude of exercise limitation. The history of cigarette smoking has an important effect on the assessment of impairment from asbestos.

In plain English

This retrospective study looked at 146 men referred by the U.S. Department of Labor between 1979 and 1983 after work mainly at shipyards where asbestos was used. The authors paired 73 men who had never smoked with 73 current smokers of similar age, years of asbestos work and estimated dust level. Smokers had worse breathing test results. Of the 73 smokers, 23 had an FEV1/VC ratio, a sign of airway obstruction, below the normal range, compared with 3 of the 73 nonsmokers. The differences persisted after pairs with obstruction or with fibrosis on chest X-ray were removed. In cycle exercise testing, 33 of 73 smokers and 15 of 73 nonsmokers reached less than 80% of predicted maximal oxygen uptake. Of those 33 smokers, 16 were judged limited by heart disease and 2 by airway obstruction. The authors concluded that cigarette smoke was by far the major contributing factor to obstructive lung disease in these workers. They noted that the study was retrospective and that self-referred workers could bias the results.

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: Retrospective matched comparison of never-smoking and currently smoking asbestos-exposed workers (lung function tests, chest X-rays, incremental cycle exercise tests)
• Who was studied: Of 348 men referred by the U.S. Department of Labor between 1979 and 1983 to Harbor-UCLA Medical Center (Torrance, California), 73 never-smokers were matched with 73 current smokers (chosen from 98 current smokers), giving 146 men. All current smokers had at least 8 pack-years of smoking.
• Exposure: Past work, mainly at shipyards where asbestos was installed, removed or otherwise used. The fiber type was not specified. Exposure was recorded as years of work (mean 22.5 years in both groups) and a subjective light, moderate or heavy rating based on visible dust. Most subjects were not currently exposed.
• Main results:
  • Vital capacity was significantly lower in the smokers. Table 2 also shows lower FEV1 and FEV1/VC in the smokers (p less than 0.05).
  • FEV1/VC was below the normal range in 3 of 73 nonsmokers and 23 of 73 smokers.
  • FEF25-75 was abnormal in 0 of 70 nonsmokers and 12 of 70 smokers. It identified no additional obstructed subjects beyond those found by FEV1/VC.
  • Diffusing capacity (DLCO) and DLCO/VA were significantly lower in the smokers.
  • The differences between smokers and nonsmokers persisted after removing the 23 pairs with an obstructed smoker, and separately after removing the 21 pairs in which either member had fibrosis on chest X-ray.
  • Interstitial fibrosis was seen on chest X-ray in 9 of 73 nonsmokers and 15 of 73 smokers. This difference was not statistically significant.
  • Among those with fibrosis, 1 of 9 nonsmokers and 10 of 15 smokers were in ILO Categories 2 or 3.
  • Maximal heart rates during exercise were similar in the two groups.
  • Maximal oxygen uptake was 2.05 plus or minus 0.54 L/min in the 73 nonsmokers and 1.77 plus or minus 0.49 L/min in the smokers (p less than 0.05). This was on average 92% versus 79% of predicted.
  • Oxygen-pulse at maximal exercise was 13.9 plus or minus 2.8 ml/beat in nonsmokers and 12.0 plus or minus 2.6 ml/beat in the 73 smokers (p less than 0.05).
  • An abnormal alveolar-arterial oxygen difference (above 30 mmHg) at maximal exercise was significantly more frequent in the smokers.
  • Maximal oxygen uptake was below 80% of predicted in 15 of 73 nonsmokers and 33 of 73 smokers (p less than 0.05). Of the 33 smokers, 16 were judged to be limited by cardiac disease and 2 by obstructive airway disease. According to Table 9, 7 of the nonsmokers were judged cardiac-limited and 3 musculoskeletal-limited.
• The authors' conclusion: The authors concluded that cigarette smoke was by far the major contributing factor to obstructive lung disease in these asbestos-exposed workers. They also concluded that smoking was associated with poorer cardiovascular function and with abnormal blood gases during exercise, which may not always be attributable solely to asbestos disease. They stated that smoking history deserves close attention when evaluating occupational impairment.
• Limitations the authors state:
  • The study was retrospective.
  • Some workers were self-referred because of symptoms or awareness of exposure, which could bias subject selection.
  • The light, medium or heavy exposure rating was a limited, subjective estimate.
  • The number of subjects was too small to draw conclusions about smoking, asbestos and fibrosis.
  • The authors could not assess differences in physical activity or conditioning between smokers and nonsmokers.

Topics

Medical terms in this study, explained in our Lexicon: Obstructive Lung Disease, Asbestos Exposure, FEV1, Diffusing Capacity (DLCO).

Related studies

• Effects of smoking on respiratory function and exercise performance in asbestos workers — X. Wang, S. Araki, et al. (1995)
• Relation between lung function, exercise capacity, and exposure to asbestos cement — P. Wollmer, L. Eriksson, et al. (1987)
• Lung function impairment as a guide to exercise limitation in work-related lung disorders — J.E. Cotes, J. Zejda, et al. (1988)
• Exercise performance and functional impairment in asbestos-exposed workers — J. Pearle (1981)
• Exercise alveolar-arterial oxygen pressure difference in interstitial lung disease — C. Risk, G.R. Epler, et al. (1984)
• 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)

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