Jill E. Jansen1, Tijmen van der Ent1, Bas J. Schouwenberg1, Cees J. Tack1, Getty Huisman-de Waal1, Rick I. Meijer1
1Radboud University Medical Centre, Nijmegen, the Netherland
E-mail address presenting author: jill.jansen@radboudumc.nl
Background
Hybrid Closed Loop (HCL) systems combine an insulin pump, real-time continuous glucose monitoring (rt-CGM), and an algorithm that automatically adjusts insulin delivery. Although randomized controlled trials have demonstrated improvements in glycaemic control, the applicability of these findings to Dutch clinical practice is uncertain because access to rt-CGM and HCL therapy is restricted to selected patient groups. This study evaluated changes in glycaemic control after initiation of HCL therapy in adults with type 1 diabetes mellitus (T1DM) treated at a tertiary care Diabetes Center and explored differences between HCL systems.
Methods
A retrospective chart review was performed in adults with T1DM who initiated an HCL system between 2021 and 2025. Glycaemic outcomes before HCL initiation and after six months of use were compared, and HbA1c changes were analysed across different HCL systems.
Results
Of 194 screened patients, 83 met the inclusion criteria (mean age 48±16 years, 75% female, diabetes duration 27±15 years). Mean HbA1c decreased significantly from 66±12 to 57±9 mmol/mol after six months of HCL use (ΔHbA1c -9 mmol/mol, p<0.001). Time in range (3.9–10.0 mmol/L) increased from 48±20% to 70±11% (p<0.001). Median glucose decreased from 10 (IQR 9–13) to 9 mmol/L (IQR 8–10; p<0.001), while glucose variability decreased from 36±7% to 34±7% (p=0.039). Time below range decreased from 2% (IQR 0–4) to 1% (IQR 0–3), although this was not statistically significant (p=0.113). Total daily insulin dose decreased from 52 (IQR 33–60) to 46 units/day (IQR 34–57), without reaching statistical significance (p=0.070).
A significant difference in HbA1c change was observed between HCL systems (p=0.007). The largest median HbA1c reduction was observed with Tandem Control-IQ (-15 mmol/mol, IQR -26 to -9), followed by CamAPS (-12 mmol/mol, IQR -20 to -6), whereas Smartadjust showed a smaller reduction (-6 mmol/mol, IQR -8 to -1). Post-hoc analyses demonstrated that Smartadjust differed significantly from the other systems (p<0.001).
Discussion/Conclusion
In this real-world cohort of adults with T1DM, HCL therapy was associated with significant and clinically relevant improvements in glycaemic control, including lower HbA1c, higher time in range, and reduced glucose variability, without increasing hypoglycaemia. Differences in HbA1c improvement were observed between HCL systems, suggesting that system-specific characteristics may influence treatment outcomes. Further studies with larger and more balanced cohorts are needed to confirm these findings.