Time in Tight Range Versus Time in Range for Predicting Diabetic Retinopathy in Adults with Type 1 Diabetes Using...

Time in tight range (TITR, 70-140 mg/dL) has emerged as a glycemic metric offering stricter assessment than conventional time in range (TIR, 70-180 mg/dL). Whether TITR provides additional prognostic value for diabetic retinopathy (DR) in adults with type 1 diabetes (T1D) remains unclear.

We conducted a retrospective cohort study of 309 adults with T1D on multiple daily insulin injections using intermittently scanned continuous glucose monitoring (CGM) system. Ophthalmological assessments were performed at baseline and after 12 months (May 2024-May 2025). DR incidence (in those free of DR at baseline) and progression (in those with established DR) were defined according to Early Treatment Diabetic Retinopathy Study criteria. Longitudinal TITR and TIR were extracted every 14-28 days. Multivariable logistic regression adjusted for age, sex, diabetes duration, HbA1c, hypertension, Low-density lipoprotein (LDL) cholesterol, body mass index, and smoking was applied.

At baseline, 198 participants (64.1%) had no DR, 71 (23.0%) nonproliferative, and 40 (12.9%) proliferative DR. During follow-up, 10/198 (5.1%) developed DR and 26/111 (23.4%) with baseline DR progressed. Higher TITR was independently associated with lower risk of incident DR (adjusted OR per % increase: 0.965; 95% CI: 0.950-0.980), whereas TIR was not. Receiver operating characteristic analysis confirmed superior discrimination for TITR versus TIR (area under the curve 0.580 vs. 0.430; P < 0.001). In stratified analyses, TITR predicted incident DR only among participants with HbA1c below the cohort median (7.1%). Both TITR and TIR were associated with lower risk of DR progression in models including HbA1c, with similar discriminative performance. Diabetes duration, HbA1c, hypertension, and smoking were independently associated with DR outcomes alongside CGM metrics.

TITR provides modestly superior predictive value over TIR for incident DR, particularly in individuals with near-target HbA1c, but both metrics perform similarly for predicting progression. CGM-derived metrics should be interpreted in the context of overall glycemic control and clinical risk factors.