Pulmonary tuberculosis and lung cancer mortality in a historical cohort of workers with asbestosis

Abstract

To examine pulmonary tuberculosis (PTB) infection and lung cancer mortality among workers with asbestosis in Hong Kong. Historical cohort study. All 124 male incident cases of asbestosis registered at the Pneumoconiosis Clinic of the Tuberculosis and Chest Service of the Department of Health between 1981 and 2008 were recruited and followed-up until 2008 to ascertain vital status and underlying causes of death. Standardized mortality ratios (SMRs) were calculated using the person-year method. Axelson's indirect method was used to adjust for the potential confounding effect of cigarette smoking. Forty-five patients (36.29%) had a history of PTB at the time of asbestosis diagnosis. The SMR of lung cancer was 5.22 [95% confidence interval (CI) 1.08-15.25] for subjects with a history of PTB, and this was reduced to 2.35 (95% CI 0.49-6.85) after indirect adjustment for smoking. Among asbestosis workers without a history of PTB, the SMR after indirect adjustment for smoking was 4.25 (95% CI 1.55-9.25) and 5.92 (95% CI 1.92-13.79) for those with comorbidities and those without comorbidities, respectively. Compared with other workers, those with a history of PTB had the highest all-cause SMR (6.73, 95% CI 4.55-9.63) and very high mortality due to heart diseases. This historical cohort study revealed that the prevalence of PTB infection was high among workers with asbestosis in Hong Kong. An excess risk of lung cancer mortality was observed among workers with a history of PTB, but the risk was lower than that seen among workers without a history of PTB. These interesting findings need to be confirmed by future studies.