Effects of Initiating Insulin Pump Therapy in the Real World: A Quasi-Experimental, Register-Based Study of Adults with Type 1 Diabetes

Background: In most randomised controlled trials among people with type 1 diabetes, insulin pump therapy (IPT) reduces HbA 1c and, in some trials, reduces the risk of diabetic ketoacidosis (DKA) and severe hypoglycaemia (SH), compared with multiple daily insulin injections (MDI). We aimed to replicate these findings using real-world data.Methods: In a quasi-experimental study of all adults with type 1 diabetes in Denmark in 2010-2020, we identified exposure to IPT and MDI using national registry data. We estimated the average treatment effect on the treated (ATT) for HbA 1c, HbA 1c variability, and risk of DKA and SH hospitalisations using a doubly robust difference-in-differences estimator. Subgroup analyses examined ATTs by demographic, socioeconomic, and health characteristics.Findings: The study population consisted of 24,623 adults with type 1 diabetes with a collective 243,601 person-years of observation; 38,823 (16%) were insulin pump-treated person-years. We identified an ATT for HbA 1c of -3·6 mmol/mol (95% CI -4·2 to -2·9; 0·33% [95% CI -0·38 to -0·27]) that was sustained up to ten years. Treatment effects were larger among women and individuals who were older, had highest baseline HbA 1c , and used continuous glucose monitoring. The ATT for HbA 1c variability corresponded to a 6·5% decrease in the within-individual standard deviation of HbA 1c . ATTs for DKA and SH corresponded to 0·52 additional and 0·1 fewer hospitalisations per 1000 person-years, respectively.Interpretation: In a real-world setting, IPT significantly reduced HbA 1c level and variability but marginally increased the risk of DKA, compared with MDI.Funding Information: This study was supported by the Steno Diabetes Center Copenhagen.Declaration of Interests: K.P.M., I.W.T and K.R. own shares in Novo Nordisk. U.P.B. sits on advisory boards for Novo Nordisk and Sanofi Aventis, has received speaker’s honorarium from Novo Nordisk and Sanofi Aventis, and has received research grants from Novo Nordisk. K.N. serves as an adviser to Medtronic, Abbott, and Novo Nordisk. She owns shares in Novo Nordisk, has received research grants to her institution from Novo Nordisk, Medtronic, Dexcom, Zealand Pharma and Roche Diabetes Care, and has received lecture fees from Medtronic, Roche Diabetes Care, Rubin Medical, Sanofi, Novo Nordisk, Zealand Pharma, and Bayer AG.Ethics Approval Statement: The study was approved by the Danish Data Protection Agency (P-2019-812), exempted from review by the Capital Region of Denmark’s Research Ethics Committee (19080899) under the National Danish Research Ethics Committe, and conducted in accordance with the Helsinki Declaration of 1964 and its later amendments.