Reduced lung function in smokers in a lung cancer screening cohort with asbestos exposure and pleural plaques

Our plain-English summary of Reduced lung function in smokers in a lung cancer screening cohort with asbestos exposure and pleural plaques, by S. Lopatin, J.C. Tsay, D. Addrizzo-Harris, et al (American Journal of Industrial Medicine, 2016).

The study

• Authors: S. Lopatin, J.C. Tsay, D. Addrizzo-Harris, J.S. Munger, H. Pass, W.N. Rom
• Journal: American Journal of Industrial Medicine
• Published: 2016;59(3):178-85
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: While low dose computed tomography (LDCT) screening for lung cancer is recommended for high-risk smokers, ages 55-74 years, information about asbestos exposure may not be routinely elicited. Asbestos exposure is associated with declining respiratory function over time; however, the effect of a history of asbestos exposure in LDCT screening cohorts is limited. We report the relationship between asbestos exposure and pulmonary function in a cohort of heavy smokers with a history of occupational asbestos exposure, hypothesizing that these subjects will have additional decreased pulmonary function. We also examined relationships between spirometric measurements and the presence of isolated pleural plaques.

Methods: A cross-sectional study was performed using data from the NYU Lung Cancer Biomarker Center cohort to compare study subjects with a history asbestos exposure primarily in the period since 1970 when tighter federal standards were in place (n = 359) to those without asbestos exposure (n = 1038) with respect to pulmonary function, LDCT lung imaging findings, and clinical symptoms. We further classified individuals with asbestos exposure by length of exposure time to examine the effect of duration of exposure on pulmonary function. Lastly, for asbestos-exposed participants, we examined the association of spirometric measurements with the presence of absence of isolated pleural plaques.

Results: Individuals with asbestos exposure had decreased FVC % predicted compared to those with no asbestos exposure (76% vs. 85% predicted, P < 0.01) and FEV1 % predicted (64% vs. 67% predicted, P < 0.01). Since there was no change in FEV1 /FVC ratio, the findings are consistent with restrictive impairment. Those with ≥20 years of exposure had a lower mean FVC % predicted compared to those with less than 20 years of exposure (74% vs. 78% predicted, P = 0.017). Individuals with asbestos exposure were more likely to have pleural plaques (P < 0.001) on CT. Those with isolated pleural plaques had lower mean % predicted FEV1 (P = 0.005) and FVC (P = 0.001) compared to those without pleural plaques.

Conclusions: Occupational asbestos exposure in a cohort of heavy smokers was associated with a significant restrictive decline in pulmonary function, with longer duration of exposure associated with greater decline. The presence of isolated pleural plaques was also associated with reduced lung function.

© 2016 Wiley Periodicals, Inc.

In plain English

This cross-sectional study examined 1,397 heavy smokers over age 50 (at least 20 pack-years) in a New York University lung cancer screening cohort, 2001 to 2013. It compared 359 asbestos-exposed people with 1,038 unexposed people. Exposure was assigned from job history (such as boiler maintenance, electrical or construction work) or self-report. Fiber types were not reported. Exposed people had lower average lung function: FVC 76% versus 85% of predicted, FEV1 64% versus 67%. The FEV1/FVC ratio did not differ, which the authors said fits a restrictive pattern. Those exposed for at least 20 years had lower FVC than those exposed for less time (74% vs. 78% predicted). Exposed people were more likely to have pleural plaques on CT. Among exposed people, the 26 with isolated plaques had lower FVC than the 220 with no CT abnormalities, though the article's figures for this comparison are inconsistent. Lung cancer rates did not differ significantly (11 of 359 exposed, 32 of 1,038 unexposed). The authors concluded that exposure was associated with restrictive lung function decline. They noted exposure could not be confirmed or measured.

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 using initial-visit data from a lung cancer screening cohort
• Who was studied: 1,397 heavy smokers over 50 years old, recruited with a smoking history of at least 20 pack-years, enrolled in the NYU Lung Cancer Biomarker Center study, New York, March 2001 to June 2013. The 'at least' symbol is lost in the text; the article calls this a heavy-smoking cohort. Of these, 359 were classed as asbestos-exposed and 1,038 as unexposed.
• Exposure: Occupational asbestos exposure, primarily since 1970. It was assigned from job description or self-report: U.S. Navy engineering, boiler maintenance, electrician or construction work, or non-administrative Con-Edison work, where exposure was mainly in maintaining underground wiring and steam pipes. Sixty-eight people had been told by a physician that they had asbestosis. Mean exposure duration was 22.5 years. Fiber types were not specified.
• Main results:
  • Unadjusted, exposed participants had lower FVC % predicted (76% vs. 85%) and lower FEV1 % predicted (64% vs. 67%) than unexposed participants, P less than 0.01 for both. The FEV1/FVC ratio did not differ.
  • Among exposed participants, those with at least 20 years of exposure had lower FVC % predicted than those with less than 20 years (74.0% vs. 78.1%, P = 0.017, unadjusted). There was no significant difference in FEV1 % predicted or the FEV1/FVC ratio.
  • After adjusting for gender, the lung function differences between exposed and unexposed groups were still significant. They were also present in a men-only analysis.
  • In multivariate analysis, a history of asbestos exposure was associated with FVC below 80% predicted (OR 1.92, 95% CI 1.35 to 2.74).
  • Asbestos exposure was associated with pleural plaques on CT: univariate OR 17.5 (95% CI 7.82 to 40.0, P less than 0.001), and multivariate OR 20.4 (95% CI 8.13 to 52.6).
  • Among exposed participants, the 26 with isolated pleural plaques had lower FVC % predicted than the 220 with no radiographic abnormalities (no emphysema or pleural plaques), with no difference in FEV1 or FEV1/FVC (unadjusted). The printed means are 76.4% vs. 76.8%, P less than 0.01, and conflict with the abstract.
  • Exposed participants had greater odds of phlegm production (OR 1.49, 95% CI 1.16 to 1.93). There was no significant difference in cough, wheezing or dyspnea score.
  • Lung cancer developed in 11 of 359 exposed and 32 of 1,038 unexposed participants; the proportions were not significantly different.
• The authors' conclusion: The authors concluded that occupational asbestos exposure in this heavy-smoking cohort was associated with a significant restrictive decline in lung function, with longer exposure associated with greater decline. They also concluded that isolated pleural plaques were associated with reduced lung function. They stated that asbestos exposure should routinely be asked about in lung cancer CT screening programs.
• Limitations the authors state:
  • Exposure was assigned from questionnaire job histories and expert review of job descriptions, and could not be accurately confirmed or quantified.
  • Because this was a heavy-smoking cohort with reduced lung function across all subjects, the findings may not generalize.
  • CT readings were not checked by an independent radiologist for agreement between readers.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Pleural plaques and thickening.

Medical terms in this study, explained in our Lexicon: Low-Dose CT Screening, Asbestos Exposure, Pleural Plaques, Lung Cancer, Biomarker, FEV1.

Related studies

• Dietary inflammatory index and risk of lung cancer and other respiratory conditions among heavy smokers in the COSMOS screening study — P. Maisonneuve, N. Shivappa, et al. (2016)
• Pleural plaques and lung function in the Marysville worker cohort: a re-analysis — K. Zu, G. Tao, et al. (2016)
• A systematic review of the association between pleural plaques and changes in lung function — L. Kopylev, K.Y. Christensen, et al. (2015)
• Comment on "pleural plaques and lung function in the Marysville worker cohort: a re-analysis" by Zu et al. (2016) — J.E. Lockey, K. Dunning, et al. (2017)
• CT scan screening for lung cancer: risk factors for nodules and malignancy in a high-risk urban cohort — A.K. Greenberg, F. Lu, et al. (2012)
• The relation among pulmonary function, chest roentgenographic abnormalities, and smoking status in an asbestos-exposed cohort — L. Rosenstock, S. Barnhart, et al. (1988)

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