Add-on therapy in metformin-treated patients with type 2 diabetes at moderate cardiovascular risk: a nationwide study

BACKGROUND In randomised clinical trials, glucagon-like peptide-1 receptor agonists (GLP-1 RAs) and sodium-glucose cotransporter 2 (SGLT-2) inhibitors reduced cardiovascular events in patients with type 2 diabetes (T2D) at high cardiovascular risk, as compared to standard care. However, data comparing these agents in patients with T2D who are at moderate risk is sparse. METHODS From Danish national registries, we included patients with T2D previously on metformin monotherapy, who started an additional glucose-lowering agent [GLP-1 RA, SGLT-2 inhibitor, dipeptidyl peptidase-4 (DPP-4) inhibitor, sulfonylurea (SU), or insulin] in the period 2010-2016. Patients with a history of cardiovascular events [heart failure (HF), myocardial infarction (MI) or stroke] were excluded. Patients were followed for up to 2 years. Cause-specific adjusted Cox regression models were used to compare the risk of hospitalisation for HF, a composite endpoint of major adverse cardiovascular events (MACE) (MI, stroke or cardiovascular death), and all-cause mortality for each add-on therapy. Patients who initiated DPP-4 inhibitors were used as reference. RESULTS The study included 46,986 T2D patients with a median age of 61 years and of which 59% were male. The median duration of metformin monotherapy prior to study inclusion was 5.3 years. Add-on therapy was distributed as follows: 13,148 (28%) GLP-1 RAs, 2343 (5%) SGLT-2 inhibitors, 15,426 (33%) DPP-4 inhibitors, 8917 (19%) SUs, and 7152 (15%) insulin. During follow-up, 623 (1.3%, range 0.8-2.1%) patients were hospitalised for HF-hazard ratios (HR) were 1.11 (95% CI 0.89-1.39) for GLP-1 RA, 0.84 (0.52-1.36) for SGLT-2 inhibitors, 0.98 (0.77-1.26) for SU and 1.54 (1.25-1.91) for insulin. The composite MACE endpoint occurred in 1196 (2.5%, range 1.5-3.6%) patients, yielding HRs of 0.82 (0.69-0.97) for GLP-1 RAs, 0.79 (0.56-1.12) for SGLT-2 inhibitors, 1.22 (1.03-1.49) for SU and 1.23 (1.07-1.47) for insulin. 1865 (3.9%, range 1.9-9.0%) died from any cause during follow-up. HRs for all-cause mortality were 0.91 (0.78-1.05) for GLP-1 RAs, 0.79 (0.58-1.07) for SGLT-2 inhibitors, 1.13 (0.99-1.31) for SU and 2.33 (2.08-2.61) for insulin. CONCLUSION In a nationwide cohort of metformin-treated T2D patients and no history of cardiovascular events, the addition of either GLP-1 RA or SGLT-2 inhibitor to metformin treatment was associated with a similar risk of hospitalisation for HF and death, and a lower risk of MACE for GLP-1 RA when compared with add-on DPP-4 inhibitors. By contrast, initiation of treatment with SU and insulin were associated with a higher risk of MACE. Additionally, insulin was associated with an increased risk of all-cause mortality and hospitalisation for HF.