Lung function predicts mortality: 10-year follow-up after lung cancer screening among asbestos-exposed workers

Our plain-English summary of Lung function predicts mortality: 10-year follow-up after lung cancer screening among asbestos-exposed workers, by T. Vehmas, P. Pallasaho, P. Piirilä (International Archives of Occupational and Environmental Health, 2013).

The study

• Authors: T. Vehmas, P. Pallasaho, P. Piirilä
• Journal: International Archives of Occupational and Environmental Health
• Published: 2013;86(6):667-72
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Purpose: To assess the predictive value of lung function impairment on mortality among asbestos-exposed workers.

Methods: A total of 590 workers originally screened for occupational lung disease including spirometry and pulmonary diffusing capacity measurements were followed up for mortality data (ICD-10 classification). The mean follow-up time was 10.5 years. Associations of different lung function parameters with mortality from all causes and from cardiovascular (I00-I99) and non-malignant respiratory diseases (J00-J99) were analysed. Factor analysis was used to create obstructive and restrictive factors.

Results: A total of 191 deaths were found altogether. Most measured lung function variables were associated with increased mortality when studied separately. Both decreased forced expiratory flow in one second (hazard ratio/measurement unit = 0.977, 95 % CI 0.969-0.988, p < 0.001) and impaired diffusing capacity (0.973, 0.965-0.981, p < 0.001) were independently associated with mortality from all causes, as well as from cardiovascular and non-malignant respiratory diseases. Both obstructive factor alone and the sum of obstructive and restrictive factors were associated with all studied mortality categories. The restrictive factor alone was associated with all-cause and respiratory mortality.

Conclusions: Deteriorated lung function predicts deaths. The reasons for impaired lung function should be medically explored to enable restoring measures aiming thus to prevent premature deaths.

In plain English

This Finnish study followed 590 asbestos-exposed construction workers (580 men, 10 women) who had been screened for occupational lung disease and lung cancer in 1996–1997. They had been invited because of a previous asbestosis diagnosis, or pleural plaques plus at least 10 pack-years of smoking. At screening, their breathing was tested, including FEV1 (air blown out in one second) and diffusing capacity, DL,CO (how well the lungs pass gas into the blood). Deaths were traced in the national register over a mean of 10.53 years. There were 191 deaths, including 64 cardiovascular and 25 from non-cancer respiratory disease. After adjusting for age, sex, body mass index, smoking and years of asbestos exposure, poorer lung function was associated with higher risk of death. FEV1 and DL,CO remained independent predictors of all-cause, cardiovascular and non-cancer respiratory deaths. The authors cautioned that this selected, mostly male group may differ from others and that the effects of asbestos and smoking could not be separated. They concluded that follow-up should include both spirometry and DL,CO.

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: Follow-up (cohort) study of mortality after a lung cancer screening study, analysed with Cox proportional hazards regression
• Who was studied: 590 asbestos-exposed construction workers (580 men, 10 women) living in the Helsinki area, Finland. They were screened in 1996–1997, and deaths were tracked to the end of 2007 comprehensively, with less complete coverage into 2009. Mean age at screening was 63 years (range 38–81). 18 were never smokers, 407 ex-smokers and 163 current smokers.
• Exposure: Occupational asbestos exposure in construction work. Fiber types are not specified. Mean duration of exposure was 26 years (range 2–48). Workers were included if they had a previous asbestosis diagnosis (n = 85), or pleural plaques without asbestosis plus a smoking history of at least 10 pack-years. The study variables were lung function measures (FEV1, FVC, FEV1/FVC, MEF50, TLC, DL,CO, DL,CO/VA), expressed as percent of predicted values.
• Main results:
  • Among the 590 workers there were 191 deaths: 64 cardiovascular, 56 cancer or neoplasm, 25 non-cancer respiratory and 46 from other causes.
  • Each lung function variable studied separately (adjusted for sex, age, body mass index, pack-years and asbestos exposure years) significantly predicted all-cause deaths. Hazard ratios were below 1.0, meaning better lung function went with a lower hazard of death.
  • For all-cause mortality, the hazard ratio per percentage point of predicted FEV1 was 0.977 (95% CI 0.969 to 0.984). For DL,CO it was 0.973 (95% CI 0.965 to 0.981).
  • In backward elimination models, FEV1 and DL,CO remained independent predictors of all-cause, cardiovascular and non-cancer respiratory deaths.
  • Some measures were not significant predictors. TLC did not significantly predict cardiovascular or non-cancer respiratory deaths, and FEV1/FVC did not significantly predict cardiovascular deaths.
  • The obstruction factor and the combined obstruction-plus-restriction factor were associated with all-cause, cardiovascular and respiratory deaths. The restriction factor was associated with all-cause and respiratory deaths but not significantly with cardiovascular deaths (HR 0.784, 95% CI 0.600 to 1.025, p 0.075).
• The authors' conclusion: The authors concluded that asbestos-exposed workers should be followed up with both spirometry and DL,CO measurements to assess disease status and prognosis. They added that any reason for poor lung function should be looked for, to enable measures aimed at preventing premature deaths.
• Limitations the authors state:
  • Data on the intensity of asbestos exposure were missing and there were few non-smokers, so the effects of asbestos and smoking could not be separated.
  • Workers were selected for signs of asbestos exposure, asbestosis and smoking history. The relationships found may therefore differ from those in the general population or in other asbestos workers.
  • The cohort was selected and male-dominated, so generalizing to the normal population should be done with care.
  • A few deaths may have been missed before data collection ended.
  • The helium dilution method may underestimate TLC when obstruction is present, and body plethysmography measurements were not available.

Topics

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

Medical terms in this study, explained in our Lexicon: Low-Dose CT Screening, Occupational Lung Disease, Spirometry, Diffusing Capacity (DLCO), Hazard Ratio.

Related studies

• Lung and pleural CT signs predict deaths: 10-year follow-up after lung cancer screening of asbestos-exposed workers — T. Vehmas, P. Oksa, et al. (2012)
• Visually scored calcifications in thoracic arteries predict death: follow-up study after lung cancer CT screening — T. Vehmas (2012)
• Extended mortality follow-up among men and women in a U.S. furniture workers union — B.A. Miller, A. Blair, et al. (1994)
• All-cause and cause specific mortality in a cohort of 20 000 construction workers; results from a 10 year follow up — V. Arndt, D. Rothenbacher, et al. (2004)
• Follow-Up of the Libby, Montana Screening Cohort: A 17-Year Mortality Study — T.C. Larson, L. Williamson, et al. (2020)
• Chest HRCT signs predict deaths in long-term follow-up among asbestos exposed workers — T. Vehmas, P. Oksa (2014)

Browse more research in International Archives of Occupational and Environmental Health, or return to medical research.