Khat and Alcohol Use Disorders Predict Poorer Adherence to Anti-Tuberculosis Medications in Southwest Ethiopia: A Prospective Cohort Study

Introduction: Tuberculosis is one of the infectious diseases causing public health crisis in low income countries and it remained among the top ten causes of mortality. Non-adherence to anti tuberculosis (anti-TB) medication greatly contributes to the rise in multi-drug resistance tuberculosis which is associated with high rates of mortality. Substance use is frequently seen among patients with poor adherence, however, little is known about the effect of substance use on adherence to anti-TB medications in Ethiopia. Therefore, we aimed to assess the effect of substance use disorders on adherence to anti-TB medications in Southwest Ethiopia. Methods: A prospective cohort study was conducted among 268 patients with tuberculosis attending services at 26 health institutions in Southwest Ethiopia between October 2017 and October 2018. A structured questionnaire translated to local language was used to assess substance use disorders, adherence and other potential risk factors for non-adherence. Patients were followed for six months and data were collected on three occasions during the follow-up. Generalized linear mixed model was used to identify the effect of substance use disorder on adherence to anti-TB medications. The model fitting was checked using Bayesian Information Criterion (BIC) while the covariate selection was based on a directed acyclic graph (DAG). Results: The overall prevalence of non-adherence among patients with substance use disorders was 16⋅4% (n=22), 41⋅7 % (n=48), and 45⋅7% (n=59) at baseline, two month, and six month respectively. The odds of non-adherence to anti-TB medications among patients with khat use disorder was nearly four times that of patients who did not use khat (aOR 3⋅8, 95%CI=1⋅8-8⋅0). Also patients who have alcohol use disorder were 3⋅2 times likely to have poor adherence compared to their counterparts (aOR=3⋅2, 95%CI=1⋅6-6⋅6). In addition, being educated (aOR =4⋅4, 95%CI=1⋅7-11⋅3), and being merchant (aOR=6⋅1, 95%CI=1⋅2-3⋅0) were associated with non-adherence to anti-TB medications. Interpretation: Khat and alcohol use disorders predict greater likelihood of non-adherence to anti-TB medication. This implies that there is a need to integrate management for substance use disorders into the existing tuberculosis treatment services. Funding Statement: Jimma University and IPPG. Declaration of Interests: All authors declare that they have no conflict of interests. Ethics Approval Statement: Ethical clearance was obtained from the Ethical Review Board of Jimma University (IHRPGC1095/2017) and LMU (Nr: 18-017). The study was discussed in detail and written informed consent was obtained from each participants. The anonymity of the study participants was kept at all stages of data processing and write-up of the manuscript.