Abstract Background Metformin’s effects on the risk of cardiovascular diseases in patients with type 2 diabetes mellitus require additional exploration. This study investigated whether metformin use in patients with type 2 diabetes mellitus would affect the risk of stroke, ischemic heart disease and peripheral arterial disease. Methods A total of 154,190 patients with newly diagnosed type 2 diabetes mellitus and having been prescribed antidiabetic drugs for 2 or more times during 1999-2005 were enrolled from Taiwan’s National Health Insurance. Metformin ever users (n=144,334) and never users (n=9856) were followed up since January 1, 2006 until December 31, 2011 for the incidence of outcomes including stroke (International Classification of Diseases, Ninth Revision, Clinical Modification, ICD-9-CM: 430-438), ischemic heart disease (ICD-9-CM: 410-414) and peripheral arterial disease (ICD-9-CM: 250.7, 785.4, 443.81, 440-448). Cox regression incorporated with the inverse probability of treatment-weighting using propensity scores. Results Among ever users and never users, 37,666 (26.1%) and 3982 (40.4%) patients developed any of the outcomes. The respective hazard ratios (95% confidence intervals) comparing ever to never users for any outcomes, stroke, ischemic heart disease and peripheral arterial disease were 0.547(0.529-0.565), 0.582 (0.552-0.614), 0.566 (0.542-0.591) and 0.655 (0.618-0.695). A dose-response pattern was observed for all analyzed outcomes in terms of cumulative duration of metformin therapy and cumulative dose of metformin therapy. Conclusions Metformin use is associated with a reduced risk of stroke, ischemic heart disease and peripheral arterial disease and any of the outcomes.
C H Tseng (Sat,) studied this question.