Emphysema findings associated with heavy asbestos-exposure in high resolution computed tomography of finnish construction workers

Our plain-English summary of Emphysema findings associated with heavy asbestos-exposure in high resolution computed tomography of finnish construction workers, by O. Huuskonen, L. Kivisaari, A. Zitting, et al (Journal of Occupational Health, 2004).

The study

• Authors: O. Huuskonen, L. Kivisaari, A. Zitting, S. Kaleva, T. Vehmas
• Journal: Journal of Occupational Health
• Published: 2004;46(4):266-71
• Cited by: 24 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Asbestos fibers are known to cause lung fibrosis, but their role in emphysema is unclear. We wanted to evaluate the relationship between asbestos exposure and emphysema by using high-resolution computed tomography (HRCT). Conventional and high resolution CT was performed on 600 smoking construction workers with an asbestos-related occupational disease. Emphysema subtypes (centrilobular, paraseptal, panlobular emphysema and bullae) were separately scored on a semiquantitative scale from 0 to 5, which scores were added up to yield the total emphysema score. Occupation, exposure duration, age, pack years and asbestosis diagnosis were analyzed in general linear models for possible associations with emphysema. The inter- (quadratic weighted kappa, kappa(qw)=0.46-0.72) and intraobserver (kappa(qw)=0.78-0.94) agreements for the subtype-scores and the reliability of the total score (Cronbach's alpha=0.87) were good. Insulators had a significantly higher paraseptal, panlobular and total score than the other occupational groups when adjusted for age and smoking. An asbestosis diagnosis was also a significant independent predictor of a higher total score. Emphysema was more common when workers had asbestosis or were heavily exposed to asbestos (insulators), but due to confounding factors the causative role of asbestos in emphysema needs further study.

In plain English

This Finnish study used high-resolution CT to look for emphysema in 600 Helsinki-area construction workers who already had an asbestos-related disease: asbestosis, or bilateral pleural plaques with at least 10 years of smoking. Workers were grouped by main occupation. Insulators, who had sprayed asbestos and dismantled asbestos insulation, were estimated to have had the heaviest exposure. Three blinded radiologists scored four emphysema subtypes. Most workers showed no emphysema; 29% had mild emphysema and 5% more severe emphysema. Smoking (pack years) was the strongest predictor of every emphysema score. After adjusting for age and smoking, all other occupational groups scored lower than insulators, but not every comparison was statistically significant; engineers, for example, did not differ significantly in panlobular or total scores. An asbestosis diagnosis independently predicted a higher total score (p=0.041). The models explained only a small share of the variation. The authors noted that possible exposure to silica or other dusts could not be defined, and that asbestosis scarring and smoking-related bronchitis were possible confounders. They concluded that the causative role of asbestos in emphysema requires further investigation.

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: Imaging study: conventional and high-resolution CT scans of asbestos-exposed workers, scored by three radiologists and analyzed with general linear models
• Who was studied: 600 Finnish construction workers (589 men, 11 women) living in the Helsinki area. They were drawn from 2,857 people with an asbestos-related occupational disease, identified in an earlier study of 18,900 asbestos-exposed Finns. Inclusion required asbestosis (n=122), or bilateral pleural plaques without asbestosis plus at least 10 years of smoking (n=488). Mean age was 64 years (range 38 to 81). Twenty subjects with asbestosis were lifetime non-smokers.
• Exposure: Occupational exposure to asbestos-containing materials in construction, for a mean of 26 years. Fiber types are not specified. Workers were classed by main occupation: engineers 41, electricians 52, carpenters 129, plumbers 74, insulators 36, others 268. Insulators (asbestos sprayers who also dismantled asbestos-containing insulation) were estimated to have the heaviest exposure. Subjects had smoked 24 pack years on average.
• Main results:
  • Across all 600 subjects, mild emphysema (total score from 0.5 up to but not including 4.5) was present in 29%. Five percent had more severe disease.
  • Smoking (pack years) was a highly significant predictor of the total emphysema score and of every emphysema subtype.
  • The text reports that occupational groups differed significantly in total score (p=0.017), paraseptal emphysema (p=0.010) and panlobular emphysema (p=0.031). Table 4, however, gives overall occupational-group p-values of 0.047 for paraseptal, 0.025 for panlobular and 0.081 for the total score.
  • In the adjusted models (Table 4), every other occupational group had lower estimated scores than insulators, but not every comparison was significant. For engineers compared with insulators, the paraseptal difference was significant (estimate -0.28, p=0.024), but the panlobular difference (p=0.17) and the total-score difference (estimate -0.81, p=0.067) were not.
  • An asbestosis diagnosis was a significant predictor of the total score (p=0.041; estimate +0.41), of centrilobular emphysema (p=0.040) and of paraseptal emphysema (p=0.018).
  • Unadjusted ('crude') total emphysema scores averaged 0.77 for workers without an asbestosis diagnosis and 1.36 for those with one.
  • The models explained only a small proportion of the variation in emphysema scores (r2 from 0.04 to 0.11). Age and years of exposure were of borderline significance at most.
  • Agreement between radiologists was 0.46 to 0.72 (quadratic weighted kappa), and agreement of each radiologist with themselves was 0.78 to 0.94. Reliability of the total score was 0.87 (Cronbach's alpha).
• The authors' conclusion: The authors concluded that there was an excess of emphysema in workers with heavy asbestos exposure and in patients with asbestosis, but that the causative role of asbestos in emphysema requires further investigation.
• Limitations the authors state:
  • Possible (and probable) exposure to silica or other dusts could not be defined.
  • Fibrosis in asbestosis shrinks and scars the lung, which may produce scar-related (cicatricial) emphysema. This might explain the link between emphysema and fibrosis scores.
  • Chronic bronchitis and emphysema from smoking can impair lung function, which may lead to a false diagnosis of asbestosis.
  • Differences between occupational groups are partly caused by individual variation.
  • Subjects were selected partly on smoking, because smoking was an inclusion criterion of the original lung cancer screening study.

Topics

Medical terms in this study, explained in our Lexicon: Emphysema, Fibrosis, Asbestos Exposure, High-Resolution CT (HRCT), Occupational Disease, Insulator, Confounding.

Related studies

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• Pulmonary function, smoking habits, and high resolution computed tomography (HRCT) early abnormalities of lung and pleural fibrosis in shipyard workers exposed to asbestos — S. Neri, P. Boraschi, et al. (1996)
• High resolution computed tomography and lung function in asbestos-exposed workers with normal chest radiographs — C.A. Staples, G. Gamsu, et al. (1989)
• Spectrum of high resolution computed tomography findings in occupational lung disease: experience in a tertiary care institute — S. Bhawna, U.C. Ojha, et al. (2013)
• Early detection of interstitial lung disease in asbestos exposed non-smoking workers by mid-expiratory flow rate and high resolution computed tomography — Z. Dujić, J. Tocilj, et al. (1991)

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