Objectives To investigate the hypothesis of an inverse relationship between intensity of asbestos exposure and mesothelioma latency among a cohort of asbestos workers in Britain.
Methods The Great Britain (GB) Asbestos Survey recruited asbestos workers attending medical examinations as required under the asbestos regulations in GB. Job details and smoking information were updated at any subsequent examinations. The primary outcome for this analysis was the time from first occupational exposure to asbestos to death with mesothelioma. Univariable and multivariable generalised gamma accelerated failure-time (AFT) models were used to estimate time ratios (TRs). Those who died with mesothelioma between 1978 and 2005 were included in the analysis.
Results After exclusions for missing data, there were 614 workers in the GB Asbestos Survey who died with mesothelioma between 1978 and 2005. Total follow-up time was 9,280 person-years, with a median latency of 22.8 years [95% confidence interval (CI) 16.0–27.2 years]. In the final multivariable AFT model, mesothelioma latency was around 26% longer for females compared to males (TR = 1.26, 95%CI = 1.15–1.37), and 5% shorter for those who died with asbestosis compared to those who did not (TR = 0.95, 95%CI = 0.91–0.99) after adjustment for year of first exposure, age at first exposure, and duration of exposure. There was no evidence of associations between mesothelioma latency and occupation, smoking status and mesothelioma type in either univariable or multivariable analyses.
Conclusions The associations between mesothelioma latency and both sex and presence of asbestosis were in the directions expected if the intensity hypothesis was true. However, there was no evidence that asbestos insulation workers, who tended to experience greater asbestos exposures than other occupations, had shorter latencies than other asbestos workers. Therefore this study did not find sufficient evidence to either support or refute the intensity hypothesis. © Crown Copyright (2012).
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