8286874 Impact of interventions to prevent asbestos-related respiratory disease in an exposed worker registry using a simplified G-computation

<h3>Background</h3> The Ontario Asbestos Workers Registry is a regulatory exposure registry obligating employers to report the number of work hours with asbestos containing materials for each of their workers. Currently, each worker is notified of the need for a medical examination once they have accrued 2,000 reported hours of work with asbestos. However, recent research showed a substantial excess of asbestos-related respiratory disease among workers in the registry indicating that the notification policy requires revision. We sought to evaluate the impact on disease prevention of alternative policies limiting asbestos work hours among registry participants using a novel application of parametric G-computation we term ‘G-POSH’. <h3>Methods</h3> A cohort of 26,164 asbestos registry workers were followed for cancer and non-malignant disease diagnoses in Ontario from 1986 through 2019. G-POSH was used to estimate decreases in disease risk under five hypothetical exposure reduction interventions. Inverse probability of censoring weighting was used to adjust for time-varying confounding due to healthy worker survivor bias. <h3>Results</h3> Standard Poisson regression analyses of the association between cumulative asbestos work hours and respiratory disease incidence rates showed substantially elevated rates well before reaching 2,000 asbestos work hours. Using G-POSH, limiting cumulative asbestos work hours to 100 hours would have reduced the risk of asbestosis by half (Risk Ratio, RR: 0.52, 95% CI 0.43-0.63) and lung cancer by 15% (RR: 0.85, 95% CI 0.78-0.92) compared to the observed natural course in the cohort. Limiting exposure to 2,000 asbestos work hours had a smaller but still substantial impact on prevention of asbestosis (RR 0.77, 95% CI: 0.70-0.86). Inverse probability weighted estimates showed a minor influence of healthy worker bias. <h3>Conclusion</h3> G-POSH is a simplified tool for estimating intervention effects in occupational cohorts. Regulatory agencies should intervene sooner to prevent respiratory disease among workers in the registry.