Effectiveness and safety of basal insulin therapy in type 2 diabetes mellitus patients with or without metformin observed in a national cohort in China

BACKGROUND: Though many randomized control trials had examined the effectiveness and safety of taking insulin therapy with or without metformin, there are limited real-world data, especially among Chinese type 2 diabetes patients initiating basal insulin (BI) with uncontrolled hyperglycemia by oral agents. This study was designed to assess the effectiveness and safety of BI therapy combined with or without metformin in a real-world national cohort study. METHODS: Patients with type 2 diabetes mellitus who initiated BI treatment due to uncontrolled hyperglycemia (HbA1c≥7 %) by oral antidiabetic drugs (OADs) were recruited in Chinese real-world settings between 2011 and 2013. A total of 12,358 patients initiated BI without bolus insulin and completed a 6-month follow-up were selected as the study population and divided into BI with metformin or BI without metformin group based on whether metformin was simultaneously prescribed or not at baseline. Propensity score adjustment was used to balance baseline covariates between two groups. A sub-analysis was also conducted among 8,086 patients who kept baseline treatment regimen during the follow-up. Outcomes were HbA1c, hypoglycemia, weight gain and insulin dose in two groups. RESULTS: 53.6 % (6,621 out of 12,358) patients initiated BI therapy concomitant with metformin. After propensity score adjustment, multivariate regression analysis controlled with number of OADs, total insulin dose, physical activity and diet consumption showed that BI with metformin group had a slightly higher control rate of HbA1c <7.0 % (39.9 % vs. 36.4 %, P = 0.0011) at 6-month follow-up, and lower dose increment from baseline to 6-month (0.0064 vs. 0.0068 U/day/kg, P = 0.0035). The sub-analysis with patients remained at same BI therapy further showed that BI with metformin group had higher HbA1c control rate (47.9 % vs. 41.9 %, P = 0.0001), less weight gain (-0.12 vs. 0.15 kg P = 0.0013), and lower dose increment during 6-month follow-up (0.0033 vs. 0.0037 U/day/kg, P = 0.0073) when compared with BI without metformin group. CONCLUSIONS: In alliance with current guidelines, the real-world findings also support the insulin initiation together with metformin. Continuous patients’ education and clinicians training are needed to improve the use of metformin when initiating BI treatment.