Impact of Age at Diagnosis and Insulin Delivery Modality on Free-Living Glycemia in Type 1 Diabetes During Periods Associated with Dysglycemia: A Retrospective Analysis of the Type 1 Diabetes Exercise Initiative Study

<b><i>Objective:</i></b> To determine the impact of age at diagnosis and insulin delivery modality on free-living glycemia in type 1 diabetes overall and during common periods of dysglycemia (sleep, post-prandially, exercise). <b><i>Research Design and Methods:</i></b> Retrospective analysis of 4 weeks' free-living data from 423 people with type 1 diabetes duration >5 years within the T1DEXI Study. Participants were divided into putative age at diagnosis endotype groups: AgeDx^<7 (diagnosed <7 years old); AgeDx^7-12 (7-12 years); AgeDx^13-30 (13-30 years); and AgeDx^>30 (>30 years). Mixed-effects linear regression, fitted with a random effect for individuals and fixed effects for age at diagnosis groups, insulin delivery modality, and duration of diabetes, was used to analyze percentage time in different glycemic states over 24 h, during sleep/exercise, and for the 2 h post-prandially. <b><i>Results:</i></b> Participants using hybrid closed-loop systems spent more time in range (TIR: 70-180 mg/dL) than those using continuous subcutaneous insulin infusion alone (<i>P</i> < 0.001) or multiple daily injections (<i>P</i> < 0.001). TIR correlated positively with age at diagnosis and increased incrementally between diagnostic age groups overall (mean ± standard deviation, AgeDx^<7: 71.4 ± 16.0%, AgeDx^13-30: 73.0 ± 13.9%; AgeDx^>30 78.3 ± 14.1%), during exercise, while sleeping and post-prandially. Linear effects modeling confirmed higher TIR in AgeDx^>30 compared with AgeDx^<7 overall (12.3%, 95% confidence interval [CI] 4.9%-19.8%, <i>P</i> = 0.0002), during exercise (13.7%, 95% CI 5.3%-22.0%, <i>P</i> = 0.0002), while sleeping (11.0%, 95% CI 3.5%-17.0%, <i>P</i> = 0.0043) and post-prandially (14.9%, 95% CI 5.9 to 23.9%, <i>P</i> = 0.0001). AgeDx^13-30 spent more TIR than AgeDx^<7 during exercise (8.3%, 95% CI 1.9%-14.7%, <i>P</i> = 0.0050). <b><i>Conclusions:</i></b> In addition to insulin modality, age at type 1 diabetes diagnosis independently impacts on glycemia in adults and should be factored into personalized care planning.