Role of Metformin in Preventing New-Onset Chronic Kidney Disease in Patients with Type 2 Diabetes Mellitus

Background: Recent evidence supports the protective role of metformin on kidney function in patients with type 2 diabetes mellitus. However, its potential to prevent new-onset chronic kidney disease (CKD) in patients with type 2 diabetes mellitus with normal renal function remains unclear. Therefore, this study aimed to investigate whether metformin could prevent the development of new-onset CKD in such patients. Methods: This retrospective, observational, multicenter cohort study included 316,693 patients with type 2 diabetes mellitus. After matching using the inverse probability of treatment weighting, 9109 metformin users and 1221 nonusers were analyzed. The primary outcomes were an estimated glomerular filtration rate (eGFR) of <60 mL/min/1.73 m², urinary albumin-to-creatinine ratio of ≥30 mg/g, and a composite outcome defined as new-onset CKD. Results: The multivariable Cox survival model showed that metformin users had significantly better renal outcomes, with a notably lower risk of sustained eGFR of <60 mL/min/1.73 m² (hazard ratio (HR), 0.71; 95% confidence interval (CI), 0.56–0.90) and new CKD onset (HR, 0.78; 95% CI, 0.65–0.94). Conclusions: Metformin plays a key role in delaying renal events in individuals with type 2 diabetes mellitus and in those with initially normal renal function.