Does faster aspart improve time in range in children with type 1 diabetes with glycaemia close to target on insulin pump therapy?

AIMS: To evaluate whether faster insulin aspart (FIA) improves time in range (TIR) compared with standard insulin aspart (SIA) in children and adolescents with type 1 diabetes achieving glycaemia close to target treated with continuous subcutaneous insulin infusion (CSII) and continuous glucose monitoring (CGM). METHODS: This prospective, open-label, randomized, 1:1 crossover trial included participants aged 6-17 years with T1D duration of ≥1 year, CSII use ≥3 months, CGM use ≥1 month, and HbA1c 64 mmol/mol (<8%). After a 2-week run-in period, they then crossed over to the alternate insulin for another 4 weeks. All participants used the same CGM system. Assessments were performed at the end of each treatment phase. The primary endpoint was the between-treatment difference in TIR (3.9-10.0 mmol/L, 70-180 mg/dL). RESULTS: Seventy-seven children were enrolled (mean T1D duration approximately 7 years; 66% male; mean HbA1c 53 mmol/mol, 7%). Mean TIR was 68.5% (SD 12.3%) with SIA and 67.6% (SD 12.1%) with FIA, with no statistically significant difference (mean difference -0.9%; 95% CI -2.60 to 0.86; P = 0.322). Similar patterns were observed for additional glycaemic metrics. Time in tight range was also similar between treatments: 46.3% for SIA versus 45.4% for FIA (P = 0.674). CONCLUSIONS: In this randomised crossover study of children and adolescents with T1D achieving glycaemia close to target on CSII, switching from SIA to FIA does not improve TIR. The absence of improvement across CGM-derived metrics suggests that FIA does not meaningfully enhance glycaemic outcomes in this clinical setting.