Smoking cessation to prevent death and tuberculosis recurrence after treatment: A prospective cohort study with a seven-year follow-up in China.

Background: Although there is consistent evidence that smoking is a risk factor associated with tuberculosis (TB), whether smoking cessation improves treatment outcomes and reduces the risk of TB recurrence remains understudied. Methods: We conducted a prospective cohort study with a seven-year follow-up in China. We recruited newly-diagnosed TB patients and classified them as non-smokers, ex-smokers, and current smokers. Current smokers were invited to participate in a smoking cessation intervention programme. We used a Cox proportional hazards model to assess the risk of death among TB patients and the risk of recurrence among successfully treated patients. Results: In total, 634 (79.2%) patients completed anti-TB treatments and 115 (14.4%) patients died. We confirmed the existence of a dose-response relationship between smoking frequency and the risk of TB recurrence (the slope of the fitted line >0; P < 0.05). Compared to those who continued smoking, the risk of death and recurrent TB for the patients who quit smoking during treatment decreased. The HR of mortality for smokers who smoked 30 or more cigarettes was 2.943 (95% confidence interval (CI) = 1.035-8.368), while the HR of mortality for those who smoked 30 or more cigarettes, but quit during treatment was 2.117 (95% CI = 1.157-3.871). However, the risk of recurrence remained high for ex-smokers who had a smoking history of 25 years or more. Conclusions: Our study provides further evidence supporting the World Health Organization's call for co-management of smoking and other risk factors as part of routine TB treatment.