Association of smoking and drug abuse with treatment failure in individuals with tuberculosis: a case-control study

Introduction: Treatment failure in tuberculosis (defined as a positive sputum smear 5 months after the initiation of anti-TB treatment) is a major threat to the control over TB. This study aimed to investigate the association of smoking and drug abuse with treatment failure among individuals with TB. Material and methods: Out of 286 TB patients with available data registered by the health system of Hamadan Provinces in western Iran, 24 TB patients with treatment failure (positive sputum smear, 5 months after initiation of anti-TB treatment) and 262 patients without treatment failure (negative sputum smear, five months after initiation of anti-TB treatment) were selected as case and control groups, respectively. These two groups were compared to each other in terms of demographic status which include age, sex, job, residence, and risk factors such as smoking and drug abuse status. An odds ratio (OR) with a 95% confidence interval was used as a measure of association. The Bonferroni correction was used to counteract multiple comparisons, therefore, a p-value of less than 0.004 was statistically significant. Results: No significant association was found between treatment failure and age, residence, comorbidity, education level, job status, sex, smoking, and method of drug abuse (P > 0.004). However, a significant association was found between duration of smoking, number of cigarettes per day, and drug abuse with treatment failure in univariate analysis (P < 0.004). In multivariate analysis, only an association with drug abuse was significantly associated with treatment failure (P = 0.047). Conclusion: Drug abuse substantially increases the risk of treatment failure. Therefore, in order to control TB, it is suggested that preventive programs are designed in order to decrease drug abuse among TB patients before starting treatment.