Comparing the Effect of Early Versus Delayed Metformin Treatment on Glycaemic Parameters Among Australian Adults With Incident Diabetes: Evidence Using a National General Practice Database

Purpose: To compare the effect of early vs delayed metformin treatment for glycaemic management among patients with incident diabetes. Methods: Cohort study using electronic health records of regular patients (1 + visits per year in 3 consecutive years) aged 40 + years with ‘incident’ diabetes attending Australian general practices (MedicineInsight, 20112018). Patients with incident diabetes were defined as those who had a) 12 + months of medical data before the f irst recording of a diabetes diagnosis AND b) a diagnosis of ‘diabetes’ recorded at least twice in their electronic medical records or a diagnosis of ‘diabetes’ recorded only once combined with at least 1 abnormal glycaemic result (i.e., HbA1c ≥ 6.5%, fasting blood glucose [FBG] ≥ 7.0 mmol/L, or oral glucose tolerance test ≥ 11.1mmol/L) in the preceding 3 months. The effect of early ( < 3 months), timely (3–6 months), or delayed (6–12 months) initiation of metformin treatment vs no metformin treatment within 12 months of diagnosis on HbA1c and FBG levels 3 to 24 months after diagnosis was compared using linear regression and augmented inverse probability weighted models. Patients initially managed with other antidiabetic medications (alone or combined with metformin) were excluded. Findings: Of 18,856 patients with incident diabetes, 38.8% were prescribed metformin within 3 months, 3.9% between 3 and 6 months, and 6.2% between 6 and 12 months after diagnosis. The untreated group had the lowest baseline parameters (mean HbA1c 6.4%; FBG 6.9mmol/L) and maintained steady levels throughout follow-up. Baseline glycaemic parameters for those on early treatment with metformin ( < 3 months since diagnosis) were the highest among all groups (mean HbA1c 7.6%; FBG 8.8mmol/L), reaching controlled levels at 3 to 6 months (mean HbA1c 6.5%; FBG 6.9mmol/L) with sustained improvement until the end of follow-up (mean HbA1c 6.4%; FBG 6.9mmol/L at 18–24 months). Patients with timely and delayed treatment also improved their glycaemic parameters after initiating ...