Mortality in a cohort of asbestos-exposed workers undergoing health surveillance

Our plain-English summary of Mortality in a cohort of asbestos-exposed workers undergoing health surveillance, by F. Barbiero, T. Zanin, F.E. Pisa, et al (La Medicina del Lavoro, 2018).

The study

• Authors: F. Barbiero, T. Zanin, F.E. Pisa, A. Casetta, V. Rosolen, M. Giangreco, C. Negro, M. Bovenzi, F. Barbone
• Journal: La Medicina del Lavoro
• Published: 2018;109(2):83-86
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: The coastal area of Friuli Venezia Giulia (FVG) region, north-eastern Italy, was characterized by work activities in which asbestos was used until the early 1990s, particularly in shipbuilding. A public health surveillance program (PHSP) for asbestos-exposed workers was established, although limited evidence exists about the efficacy of such programs in reducing disease occurrence and mortality.

Objectives: To compare mortality in a cohort of 2,488 men occupationally exposed to asbestos, enrolled in a PHSP in FVG between the early 1990s and 2008, with that of the general population of FVG and Italy.

Methods: Standardized Mortality Ratios (SMR), with 95% Confidence Interval (95% CI), for all causes, all cancers, lung (LC) and pleural cancer (PC) were estimated in the cohort and in subgroups of workers with the first hire in shipbuilding that caused asbestos exposure (<1974, 1974-1984, 1985-1994).

Results: A strong excess in mortality for PC with reference to FVG (SMR=6.87, 95% CI 4.45-10.17) and Italian population (SMR=13.95, 95% CI 9.02-20.64) was observed. For LC, the FVG-based SMR was 1.49 (95% CI 1.17-1.89) and the Italy-based 1.43 (95% CI 1.12-1.81). Mortality among workers with the first hire in shipbuilding before 1974 was high for PC (FVG-based SMR=8.98, 95% CI 5.56-13.75; Italy-based SMR=18.41, 95% CI 11.40-28.17) and for LC (FVG-based SMR =1.60, 95% CI 1.18-2.11; Italy-based SMR=1.54, 95% CI 1.14-2.03). Further, for LC between 1974 and 1984, the FVG-based SMR was 2.45 (95% CI 1.06-4.82), and the Italy-based SMR was 2.33 (95% CI 1.01-4.60).

Conclusions: This cohort experienced an excess mortality for pleural and lung cancer, compared with regional and national populations. For lung cancer, the excess was stronger in workers with the first hire in shipbuilding before 1985, suggesting a key role of asbestos exposure.

In plain English

This historical cohort study followed 2,488 men with confirmed past work exposure to asbestos. They were enrolled, up to 2008, in a public health surveillance program at an occupational medicine clinic in the coastal area of Friuli Venezia Giulia (FVG), north-eastern Italy. About 70% had worked in shipbuilding. Deaths from 1989 to 2011 were compared with numbers expected from the general populations of FVG and of Italy.

There were 25 deaths from malignant neoplasm of the pleura, against 3.64 expected from FVG rates and 1.79 from Italian rates (SMR 6.87, 95% CI 4.45-10.17, and 13.95, 95% CI 9.02-20.64). There were 70 lung cancer deaths (SMR 1.49, 95% CI 1.17-1.89, and 1.43, 95% CI 1.12-1.81). Neither deaths from all causes nor deaths from all cancers combined showed a statistically significant excess.

Among shipbuilding workers, the pleural excess was strongest in those first hired before 1974. The lung cancer excess was strongest in those first hired between 1974 and 1984. The authors concluded that this suggested a key role of asbestos exposure. They noted that follow-up began only at enrollment and that 18% of enrollees could not be linked to health records.

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: Historical (retrospective) cohort mortality study comparing a surveillance cohort with the general populations of FVG and Italy using standardized mortality ratios (SMRs)
• Who was studied: 2,488 men with previous occupational asbestos exposure, identified at a Local Health Authority occupational medicine clinic (Monfalcone area, FVG, Italy) up to 2008, followed 1989-2011 for 26,415.78 person-years; 96 women in the program were not analysed
• Exposure: Occupational asbestos exposure (fiber types not specified), individually confirmed and graded low (477), medium (1,691) or high (320) by an occupational doctor. Industries were shipbuilding (1,740), metalworking, electric, insulation and other. Mean 18.28 years of exposure.
• Main results:
  • Whole cohort, malignant neoplasm of the pleura: 25 deaths observed versus 3.64 expected (FVG rates) and 1.79 expected (Italian rates)
  • Whole cohort, pleural cancer SMR 6.87 (95% CI 4.45-10.17) based on FVG rates and 13.95 (95% CI 9.02-20.64) based on Italian rates
  • Whole cohort, lung cancer: 70 deaths; SMR 1.49 (95% CI 1.17-1.89) based on FVG rates and 1.43 (95% CI 1.12-1.81) based on Italian rates
  • Whole cohort, all causes: 388 deaths; SMR 0.89 (95% CI 0.80-0.98) based on FVG rates and 0.94 (95% CI 0.85-1.03) based on Italian rates
  • Whole cohort, all cancers: no statistically significant excess. The SMR was 0.96 (95% CI 0.83-1.11) based on FVG rates and 1.07 (95% CI 0.92-1.24) based on Italian rates.
  • Shipbuilding workers first hired before 1974 (1,370 men, 21 pleural deaths): pleural cancer SMR 8.98 (95% CI 5.56-13.75) based on FVG rates and 18.41 (95% CI 11.40-28.17) based on Italian rates
  • Lung cancer in shipbuilding subgroups: Italy-based SMR 1.54 (95% CI 1.14-2.03) for those first hired before 1974; FVG-based SMR 2.45 (95% CI 1.06-4.82) for those first hired 1974-1984 (8 deaths; Italy-based SMR 2.33, 95% CI 1.01-4.60, per Table 4)
  • Shipbuilding workers first hired 1985-1994: the pleural cancer excess was not statistically significant (136 men, 1 death); the authors attributed this to small numbers and the long latency of the disease
  • Prostate cancer mortality was lower than expected: SMR 0.09 (95% CI 0.00-0.49) based on FVG rates (1 death); the authors said results for cancers other than lung and pleura should be interpreted with caution
• The authors' conclusion: The authors concluded that, compared with the FVG and Italian populations, the cohort showed a very strong excess of pleural cancer mortality and significantly increased lung cancer mortality. They found the lung cancer excess stronger in those first hired in shipbuilding between 1974 and 1984, suggesting a key role of asbestos exposure. They attributed normal all-cause mortality partly to a healthy worker effect.
• Limitations the authors state:
  • Follow-up started only when workers entered surveillance, so the period from first exposure to enrollment is missing, which may cause selection bias
  • 18% of the persons initially enrolled were excluded because they could not be linked with the Regional Health Database, which might cause selection bias
  • The cohort is left truncated, which leads to an overestimation of effects; the authors considered this not a major issue because latency analysis was not a goal
  • The induction period for lung and pleural cancers was assumed not to be complete at enrollment, particularly for those first exposed from the mid-1980s
  • Enrollment may have depended on health status (symptoms or a cancer diagnosis). The authors excluded people with a cancer diagnosis in the regional cancer registry (1995-2009) and judged a large overestimation unlikely.
  • Excluding prevalent cancer cases may have reduced comparability with the general population for other cancers, so results for other cancer sites should be interpreted with caution

Topics

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

Medical terms in this study, explained in our Lexicon: standardized mortality ratio (SMR), confidence interval, Asbestos Exposure, Lung Cancer.

Related studies

• Cancer incidence in a cohort of asbestos-exposed workers undergoing health surveillance — F. Barbiero, T. Zanin, et al. (2018)
• Malignant mesothelioma due to non-occupational asbestos exposure from the Italian national surveillance system (ReNaM): epidemiology and public health issues — A. Marinaccio, A. Binazzi, et al. (2015)
• Mesothelioma trends in the United States: an update based on Surveillance, Epidemiology, and End Results Program data for 1973 through 2003 — B. Price, A. Ware (2004)
• Impact of low-dose computed tomography screening on lung cancer mortality among asbestos-exposed workers — F. Barbone, F. Barbiero, et al. (2018)
• Mortality among British asbestos workers undergoing regular medical examinations (1971-2005) — A.H. Harding, A. Darnton, et al. (2009)
• Geographic study of mortality due to mesothelioma in Peru and its evolution — J.S. Torres-Roman, V. Gomez-Rubio, et al. (2020)

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