Comparative Effects of Metformin and Dipeptidyl Peptidase-4 Inhibitors in Japanese Obese Patients with Type 2 Diabetes: A Claims Database Study

Introduction Metformin has demonstrated favorable effects on glycemic control in patients with type 2 diabetes (T2D), regardless of the body mass index (BMI). On the contrary, dipeptidyl peptidase-4 inhibitors (DPP-4is) are reportedly less effective in patients having high BMI values (>= 25 or >= 30). The aim of this study was to compare metformin and DPP-4is as first-line treatment for their effects on glycemic control and improvement of other health outcomes among obese and non-obese Japanese patients with T2D. Methods A Japanese health insurance claims database that also included annual medical checkup data was used. This database included data on company employees who were members of health insurance societies and their family members. Most patients were aged < 65 years and most were men. Inclusion criteria were: (1) a first T2D diagnosis between May 2010 and June 2017; (2) either metformin or a DPP-4i prescribed as the first-line antidiabetic therapy; and (3) glycated hemoglobin (HbA1c) and BMI data available for the 3-month period immediately preceding the initiation of antidiabetic treatment (baseline). The reduction rate in excessive HbA1c (> 6.5%; primary outcome) and changes in fasting plasma glucose, BMI, triglyceride, cholesterol, and abdominal circumference (secondary outcomes) at 12 months from baseline were compared between treatments. Results When evaluated relative to the baseline BMI, the mean reduction rate in excessive HbA1c tended to be higher in the metformin group than in the DPP-4i group, especially in patients with BMI >= 25. Similarly, significant improvement was observed in most outcomes in obese patients prescribed metformin compared to those prescribed a DPP-4i. In contrast, in patients with BMI < 25, HbA1c reduction was greater in patients prescribed DPP-4i and fewer outcomes showed significant improvement in patients prescribed metformin. Conclusion In obese Japanese patients with T2D, greater improvements in glycemic control and other outcomes were seen with metformin as first-line treatment for T2D compared with DPP-4is, although some limitations regarding the database information should be considered.