2006 Smoking and tuberculosis among silicotic patients in Hong Kong
Dr. Ka-Wa Chan, Tuberculosis and Chest Unit, Grantham Hospital
Background
Smoking and tuberculosis are both common conditions in Hong Kong. Silicotic patients carry a higher risk for tuberculosis. On the other hand, most of the silicotic patients are also smokers.
Method
A cohort of 431 silicotic patients with no history of tuberculosis was recruited from 1995 to 2002. Tuberculin test was done with 1 unit of PPD-RT23 and these patients were followed up prospectively till the end of 2004. Baseline background and disease characteristics were analysed with positive tuberculin reaction (>=10mm) and development of disease by univariate and then multivariate analysis.
Results:
Smoking and alcohol use were independent predictors of positive tuberculin reaction at baseline in multiple logistic regression analysis (all P < 0.05). Total cigarette pack-years did not demonstrate any significant effect. The annual incidences of tuberculosis were 1683, 2296 and 4392 for never, ex- and current smokers respectively. On Cox proportional hazard analysis, current smokers carried significantly higher risk of tuberculosis than other silicotic patients (adjusted hazard ratio:1.93, 95%CI:1.09-3.43) after controlling for age, alcohol use, tuberculin status, treatment for latent TB infection, and other relevant background / disease factors. A significant dose-response relationship was also observed with the number of cigarettes currently being smoked.
Conclusion:
Smoking increases the risk of both tuberculosis infection and the subsequent development of disease among silicotic patients. Smoking cessation may reduce the chance of developing TB in silicotic patients.
