Impacts of metformin on tuberculosis incidence and clinical outcomes in patients with diabetes: A systematic review and meta-analysis

Background: Accumulating evidence suggested that the use of metformin had more benefits for both prevention and treatment of tuberculosis (TB) than non-metformin use in patients with diabetes mellitus (DM); however, it remains to be fully elucidated on this topic. Thus, we conducted a systematic review and meta-analysis of published studies to determine the association between metformin use and TB in diabetic patients. Methods and materials: The MEDLINE, EMBASE, Information Sciences Institute (ISI) Web of Science and Cochrane CENTRAL databases were searched from their inception to April 15, 2019. Studies that evaluated the use of metformin and TB disease were included. The quality of each study was evaluated through the Newcastle-Ottawa Scale (NOS). For pooled data, the relative risk (RR) and 95% CIs were calculated; otherwise, a systematic review. Results: Seventeen observational studies were included, with a low risk of bias on NOS. The meta-analysis showed that metformin use was associated with a significantly lower active TB incidence and mortality among individuals with DM (RR =0.51; 95% CI: 0.38–0.69, p ⩽ 0.001) and with TB-DM (RR = 0.34; 95% CI, 0.20–0.57, p ⩽ 0.001), respectively. Conclusion: This meta-analysis indicated metformin use brought benefits to both prevention and treatment outcomes of TB among diabetic patients. Randomized controlled trials (RCTs) are needed to confirm these associations.