Smoking increases risk of recurrence after successful anti-tuberculosis treatment: a population-based study

OBJECTIVE: To investigate whether tobacco smoking increases the risk of tuberculosis (TB) recurrence and identify factors associated with TB recurrence among adults who had successfully completed anti-tuberculosis treatment in Taipei, Taiwan. METHODS: Recurrence was defined as a new clinical or microbiological diagnosis of TB requiring the start of a new course of treatment in a patient who had satisfactorily completed treatment for a previous TB episode. Cox proportional hazard models were used to calculate adjusted hazard ratios (aHRs) for recurrence. RESULTS: We followed 5567 adults for recurrence after successful anti-tuberculosis treatment. The mean age was 58.5 years; 62.9% were male. Overall, 84 (1.5%) had a recurrence of TB during follow-up. The incidence of TB recurrence was 4.9 episodes/1000 person-years of follow-up. Cox proportional hazards regression showed that after controlling for other variables, the risk of TB recurrence among subjects who smoked >10 cigarettes a day was double that of never/former smokers. Other independent risk factors significantly associated with TB recurrence were homelessness (aHR 3.75, 95%CI 1.17-12.07), presence of comorbidities (aHR 2.66, 95%CI 1.22-5.79) and a positive acid-fast bacilli smear (aHR 2.27, 95%CI 1.47-3.49). CONCLUSION: Smoking >10 cigarettes a day was significantly associated with TB recurrence. To reduce the risk of recurrence, we recommend including effective measures of smoking cessation in TB control programmes, as recommended by the World Health Organization Stop TB Strategy.