Cardiovascular Risk Associated With Acarbose Versus Metformin as the First-Line Treatment in Patients With Type 2 Diabetes: A Nationwide Cohort Study

Context: Metformin is the first-line oral therapy for type 2 diabetes with proven benefits against cardiovascular risk. Recent evidence suggested that acarbose might be similar to metformin in glucose-lowering efficacy and cardiovascular risk reduction. Therefore, international guidelines have suggested the use of acarbose as alternative first-line antidiabetic therapy. Objective: To compare the cardiovascular outcomes in the first-line users of acarbose vs metformin. Design, Setting, Patients, and Outcome Measures: A nationwide cohort study was conducted by analyzing the Taiwan National Health Insurance (NHI) Database. A total of 17 366 acarbose initiators and 230 023 metformin initiators were identified between January 1, 2009 and December 31, 2010. The primary outcome is hospitalization due to any cardiovascular events, including acute myocardial infarction, congestive heart failure, and ischemic stroke. The propensity score method was used to adjust for baseline differences between the two groups. Patients were followed from drug initiation to the earliest of outcome occurrence, death or disenrollment from NHI, or study termination. Results: In intention-to-treat analyses, acarbose was associated with a higher risk of any cardiovascular event (adjusted hazard ratio [HR]: 1.05; 95% confidence interval [CI], 1.01-1.09), heart failure (HR, 1.08; 95% CI, 1.00-1.16), and ischemic stroke (HR, 1.05, 95% CI, 1.00-1.10) than metformin. No significant difference in risk was found in subgroups of patients with or without underlying hypertension, ischemic heart disease, or cerebrovascular disease. Similar results were found in auxiliary as-treated analyses or analyses stratified by propensity score quintiles. Conclusion: Our data do not support that acarbose has a cardio-protective effect similar to metformin as a first-line antidiabetic agent.