Dose-Normalised Time in Range (dn-TIR) Improves Following Hybrid Closed-Loop (HCL) Therapy in Type 1 Diabetes: A Real-World Cohort Study From Australia and the United Kingdom.

OBJECTIVE: To evaluate dose-normalised time in range (dn-TIR) and its log relative change (Δdn-TIR) as measures of within-person glycaemic change relative to total daily insulin exposure following hybrid closed-loop therapy (HCL/AID). RESEARCH DESIGN AND METHODS: We conducted a retrospective two-cohort study of people with type 1 diabetes commencing hybrid closed-loop/automated insulin delivery (HCL/AID) therapy in Australia and the United Kingdom (UK). dn-TIR was calculated as time in range (TIR) 3.9-10.0 mmol/L (70-180 mg/dL) divided by total daily insulin dose (TDD) and Δdn-TIR as log[(TIR/TDD)post/(TIR/TDD)pre]. RESULTS: The study comprised 86 people living with type 1 diabetes in Australia and 288 in the UK. In the fixed Australian dn-TIR cohort, TIR increased from 53.2% ± 20.7% to 70.4% ± 14.6% (n = 86; p < 0.001), whereas mean TDD changed from 53.3 to 52.0 units/day (n = 86; p = 0.724). Median Δdn-TIR was 0.224 [IQR: -0.033, 0.583]. In the UK cohort, TIR increased from a median 54% [34, 68] to 66% [54, 74] (n = 257; p < 0.001), whereas mean TDD changed from 44.1 to 46.3 units/day (n = 242; p = 0.152). Median Δdn-TIR was 0.194 [IQR: -0.097, 0.541]. CONCLUSIONS: HCL/AID therapy improved TIR relative to TDD in two real-world cohorts. dn-TIR and Δdn-TIR are not replacements for established CGM metrics or direct measures of insulin sensitivity; they may provide an adjunct longitudinal description of whether glycaemic improvement was accompanied by proportionately greater, similar or lower insulin exposure.