The latency period of mesothelioma among a cohort of British asbestos workers (1978-2005)

Our plain-English summary of The latency period of mesothelioma among a cohort of British asbestos workers (1978-2005), by G. Frost (British Journal of Cancer, 2013).

The study

• Author: G. Frost
• Journal: British Journal of Cancer
• Published: 2013;109(7):1965-73
• Cited by: 76 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: The Great Britain (GB) Asbestos Survey is a prospective cohort of asbestos workers in GB. The objective of this study was to investigate determinants of mesothelioma latency, paying particular attention to indicators of intensity of asbestos exposure such as occupation, sex, and presence of asbestosis.

Methods: The analysis included members of the cohort who died with mesothelioma between 1978 and 2005. The primary outcome was the latency period defined as the time from first occupational exposure to asbestos to death with mesothelioma. Generalised gamma accelerated failure-time models were used to estimate time ratios (TRs).

Results: After excluding missing data, there were 614 workers who died with mesothelioma between 1978 and 2005. Total follow-up time was 9280 person-years, with a median latency of 22.8 years (95% confidence interval (CI) 16.0-27.2 years). In the fully adjusted model, latency was around 29% longer for females compared with males (TR=1.29, 95% CI=1.18-1.42), and 5% shorter for those who died with asbestosis compared with those who did not (TR=0.95, 95% CI=0.91-0.99). There was no evidence of an association between latency and occupation.

Conclusion: This study did not find sufficient evidence that greater intensity asbestos exposures would lead to shorter mesothelioma latencies.

In plain English

This study examined what influences mesothelioma latency (time from first occupational asbestos exposure to death with mesothelioma) in the Great Britain Asbestos Survey, a prospective cohort of asbestos workers. The analysis covered 614 cohort members who died with mesothelioma between 1978 and 2005. With no exposure measurements available, the author used sex, occupation and death with asbestosis as indicators of exposure intensity. Among these workers, the unadjusted median latency was 22.8 years (95% CI 16.0–27.2); the fully adjusted median was 34.0 years (95% CI 32.7–35.4). In that model, latency was on average 29% longer for women than men (time ratio 1.29, 95% CI 1.18–1.42) and 5% shorter, about 2 years, for those who died with asbestosis (time ratio 0.95, 95% CI 0.91–0.99). There was no evidence that latency differed by occupation, including for insulation workers, or by smoking status. Latency was shorter for people first exposed in later years and at older ages. The author noted that deaths from other causes could be an alternative explanation for the sex and asbestosis findings. The author concluded that the study did not find sufficient evidence that more intense exposures lead to shorter latencies.

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: Analysis of a prospective occupational cohort (GB Asbestos Survey), using survival-type models (generalised gamma accelerated failure-time models) to estimate time ratios for latency
• Who was studied: Asbestos workers in Great Britain attending regular medical examinations under asbestos regulations. The survey recruited 98,912 workers from 1971 to 2005. The analysis included 614 workers with complete data who died with mesothelioma between 1978 and 2005, followed for 9280 person-years.
• Exposure: Occupational asbestos exposure, grouped by main occupation (manufacturing, removal, insulation, 'other'). The cohort collected no actual exposure measurements, and the article does not report fiber types for cohort members. Sex, occupation and death with asbestosis were treated as indicators of exposure intensity.
• Main results:
  • Unadjusted median latency among the 614 workers who died with mesothelioma was 22.8 years (95% CI 16.0–27.2 years).
  • After adjustment for all variables in the full model, the overall median latency among these workers was 34.0 years (95% CI 32.7–35.4 years).
  • In the full adjusted model, women had latencies on average 29% longer than men (time ratio 1.29, 95% CI 1.18–1.42), around a 10-year difference.
  • In the full adjusted model only, those who died with asbestosis had latencies on average 5% shorter than those who did not (time ratio 0.95, 95% CI 0.91–0.99), a difference of about 2 years.
  • There was no evidence that latency was associated with occupation. Insulation workers had a median latency of 20.3 years, compared with 24.8 years for manufacturing workers and 25.5 years for 'other' workers, but this difference was not statistically significant.
  • In the full model, main smoking status, main occupation and mesothelioma type were not statistically significantly associated with latency.
  • Latency decreased with later year of first exposure. Those first exposed in 1980 or later had 56% shorter latencies than those first exposed before 1940 (time ratio 0.44, 95% CI 0.40–0.49). Latency also decreased with older age at first exposure.
  • Median latency was 8.2 years for peritoneal mesothelioma and 22.9 years for pleural mesothelioma. The author describes these medians as highly uncertain, and the difference was not statistically significant.
• The authors' conclusion: The author concluded that the study did not find sufficient evidence that more intense asbestos exposures lead to shorter mesothelioma latencies. The sex and asbestosis findings gave some support, but sufficient doubt remains.
• Limitations the authors state:
  • Actual exposure measurements were not available; occupation, sex and asbestosis were used as proxies for exposure intensity.
  • Differences in death rates from other causes could be an alternative explanation for the associations with sex and asbestosis.
  • The occupational groups were broad, which could have weakened any association between occupation and latency.
  • The limited follow-up period may have kept the estimated median latency short; further follow-up would likely increase it.
  • For the 24 cases with latency under 10 years, the date and source of asbestos exposure are in doubt.
  • Mesothelioma type was pieced together from several sources and may often be misclassified.
  • The effect of asbestos fiber type on latency is unknown.

Topics

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

Medical terms in this study, explained in our Lexicon: Latency, Mesothelioma, Asbestos Exposure, Occupational Exposure, confidence interval.

Related studies

• Response to comment on 'The latency period of mesothelioma among a cohort of British asbestos workers (1978-2005)' — G. Frost (2014)
• Comment on 'The latency period of mesothelioma among a cohort of British asbestos workers (1978-2005)': methodological problems with case-only survival analysis — D. Consonni, F. Barone-Adesi, et al. (2014)
• Comment on 'The latency period of mesothelioma among a cohort of British asbestos workers (1978-2005)' — D. Mirabelli, D. Zugna (2014)
• Comment on 'The latency period of mesothelioma among a cohort of British asbestos workers (1978-2005)': the effect of left censoring — A. Farioli, S. Mattioli, et al. (2014)
• Occupational exposures to cosmetic talc and risk of mesothelioma: an updated pooled cohort and statistical power analysis with consideration of latency period — G.M. Marsh, A.M. Ierardi, et al. (2019)
• Letter concerning: Occupational exposures to cosmetic talc and risk of mesothelioma: an updated pooled cohort and statistical power analysis with consideration of latency period by Gary M. Marsh et al. (Inhal Toxicol. 2019 Aug 5:1-11. doi:10.1080/08958378.2019.1645768) — M.M. Finkelstein (2019)

Browse more research in British Journal of Cancer, or return to medical research.