Temporal patterns of occupational asbestos exposure and risk of pleural mesothelioma

Our plain-English summary of Temporal patterns of occupational asbestos exposure and risk of pleural mesothelioma, by A. Lacourt, K. Leffondré, C. Gramond, et al (The European Respiratory Journal, 2012).

The study

• Authors: A. Lacourt, K. Leffondré, C. Gramond, S. Ducamp, P. Rolland, A. Gilg Soit Ilg, M. Houot, E. Imbernon, J. Févotte, M. Goldberg, P. Brochard
• Journal: The European Respiratory Journal
• Published: 2012;39(6):1304-12
• Cited by: 39 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Asbestos is the primary cause of pleural mesothelioma (PM). The objective of this study was to elucidate the importance of different temporal patterns of occupational asbestos exposure on the risk of PM using case-control data in male subjects. Cases were selected from a French case-control study conducted in 1987-1993 and the French National Mesothelioma Surveillance Program in 1998-2006. Population controls were frequency matched to cases by year of birth. Occupational asbestos exposure was evaluated with a job-exposure matrix. The dose-response relationships were estimated using restricted cubic spline functions in logistic regression models. A total of 2,466 ever-asbestos-exposed males (1,041 cases and 1,425 controls) were used. After adjustment for intensity and total duration of occupational asbestos exposure, the risk of PM was lower for subjects first exposed after the age of 20 yrs and continued to increase until 30 yrs after cessation of exposure. The effect of total duration of exposure decreased when age at first exposure and time since last exposure increased. These results, based on a large population-based case-control study, underline the need to take into account the temporal pattern of exposure on risk assessment.

In plain English

This French case-control study examined how the timing of workplace asbestos exposure related to pleural mesothelioma in men. Cases were diagnosed in 1987-1993 or 1998-2006. Population controls were matched to cases by birth year. Analyses included only men ever exposed at work: 1,041 cases and 1,425 controls. Exposure was estimated from job histories using a job-exposure matrix. Cases had a higher average exposure index, combining assessed probability, frequency and intensity of exposure, than controls (0.6 versus 0.2 fibres per mL). Comparing 30 years of exposure with 1 year, the odds ratio was 7.5 (95% CI 4.2-13.4) for men last exposed 20 years earlier and 4.0 (95% CI 2.2-7.2) for men last exposed 30 years earlier. The effect of duration was also weaker in men first exposed later in life. Risk kept increasing during the first 30 years after exposure stopped. Among men exposed longer than the median 30 years, those first exposed at age 30 had lower estimated risk than those first exposed at age 10 (odds ratio 0.2, 95% CI 0.0-0.7). The authors noted they did not account for intensity changes over time or for home or environmental exposure.

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: Case-control study with population controls. Cases were pooled from a French hospital-based case-control study and the French National Mesothelioma Surveillance Program. Analysis used logistic regression with restricted cubic spline functions.
• Who was studied: Men in France who had ever been occupationally exposed to asbestos: 1,041 pleural mesothelioma cases and 1,425 controls. Cases were diagnosed 1987-1993 in five French regions or 1998-2006 in 22 French districts. Women were excluded because there were too few cases (82).
• Exposure: Occupational asbestos exposure assessed with a job-exposure matrix. The study did not analyse specific fiber types. Exposure was described by four measures. The first was the mean index of exposure (in fibres per mL), which combines the assessed probability, frequency and intensity of exposure for each job, weighted by job duration. The others were total duration of exposure, age at first exposure, and time since last exposure.
• Main results:
  • Compared with controls, cases had a higher mean index of exposure (0.6 versus 0.2 fibres per mL), a longer mean total duration of exposure (27.8 versus 24.9 years) and an earlier mean age at first exposure (21.0 versus 22.6 years).
  • Risk of pleural mesothelioma rose sharply with the mean index of exposure at lower levels and increased with a weaker slope at higher levels.
  • The effect of duration (30 years versus 1 year of exposure) was smaller the longer ago exposure ended: odds ratio 7.5 (95% CI 4.2-13.4) for men last exposed 20 years earlier, versus 4.0 (95% CI 2.2-7.2) for men last exposed 30 years earlier.
  • The effect of duration (30 years versus 1 year of exposure) was smaller with later age at first exposure: odds ratio 6.5 (95% CI 4.3-9.8) for men first exposed at age 15, versus 1.5 (95% CI 1.1-2.2) for men first exposed at age 30.
  • For all subjects, risk continued to increase during the first 30 years after exposure stopped. In men with duration shorter than 30 years, estimated risk stopped increasing after 30 years of cessation, and a slight decrease was seen after 35 years.
  • Among men with longer duration of exposure, those first exposed at age 30 had a lower estimated risk than those first exposed at age 10 (odds ratio 0.2, 95% CI 0.0-0.7). The decrease was much less pronounced in men with shorter duration.
• The authors' conclusion: The authors concluded that their findings confirm that pleural mesothelioma risk increases with intensity and duration of exposure. They also concluded that the findings suggest the effect of duration decreases with increasing time since last exposure and with later age at first exposure, and that the temporal pattern of exposure should be taken into account in risk assessment.
• Limitations the authors state:
  • The authors called this the main limitation: the analyses did not account for changes in exposure intensity over the different periods of each person's exposure.
  • The job-exposure matrix may have misclassified exposure. The authors considered this likely nondifferential, meaning some effects might have been underestimated.
  • Only occupational exposure was considered. No information on domestic or environmental asbestos exposure was available, which may have introduced confounding.
  • Cases and controls each came from two different sources, which may have introduced bias.
  • Few subjects had very long times since exposure ended. The slight decline in risk after long cessation could also reflect less intensive diagnostic procedures in those subjects.
  • Duration and time since last exposure were strongly correlated (Pearson coefficient -0.76). This inflated standard errors and widened confidence intervals for duration in model 1.

Topics

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

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Pleural Mesothelioma, Case-Control Study, Mesothelioma, Dose-response relationship.

Related studies

• Occupational and non-occupational attributable risk of asbestos exposure for malignant pleural mesothelioma — A. Lacourt, C. Gramond, et al. (2014)
• Pleural mesothelioma and occupational coexposure to asbestos, mineral wool, and silica — A. Lacourt, C. Gramond, et al. (2013)
• Attributable risk in men in two French case-control studies on mesothelioma and asbestos — A. Lacourt, P. Rolland, et al. (2010)
• Occupations and industries in France at high risk for pleural mesothelioma: A population-based case-control study (1998-2002) — P. Rolland, C. Gramond, et al. (2010)
• Co-exposure to refractory ceramic fibres and asbestos and risk of pleural mesothelioma — A. Lacourt, M. Rinaldo, et al. (2014)
• Temporal Patterns of Exposure to Asbestos and Risk of Asbestosis: An Analysis of a Cohort of Asbestos Textile Workers — A. Farioli, F.S. Violante, et al. (2018)

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