Metformin and tuberculosis risk in elderly patients with diabetes mellitus

SETTING: Tuberculosis (TB) and diabetes mellitus (DM) remain global health concerns. Metformin has recently received attention for its anti-tuberculosis effects. OBJECTIVE: To evaluate the risk of TB development in elderly DM patients treated with metformin compared with sulfonylureas. DESIGN: We performed a retrospective cohort study using the National Health Insurance Service-Senior database. The participants were type-2 DM (T2DM) patients aged ≥60 years between 1 January 2003 and 31 December 2013. We matched each metformin user to a sulfonylurea user using a propensity score. A Cox proportional hazards model was used to compare the risk of TB in metformin and sulfonylurea users. RESULTS: After propensity score matching, 12,582 patients were in each group. The TB incidence was 280.2/100 000 person-years (py) for metformin users and 394.5/100 000 py for sulfonylurea users. Metformin users had a lower risk of TB development than sulfonylurea users (adjusted hazard ratio 0.74, 95%CI 0.58-0.95), and the results were stronger for male participants. A dose-response relationship between metformin use and TB development was found in both sexes. CONCLUSION: Metformin use was associated with a decreased risk of TB development among elderly T2DM patients compared with sulfonylurea use.