Association between time in tight range and incident diabetic retinopathy in adults with type 2 diabetes

Aims: Time spent in the glucose range of 70-180 mg/dL (TIR) has become entrenched as a key measure of glycaemic control, which was linked to diabetes-related outcomes in previous studies. However, there has been a recent debate about whether to instead emphasize time in the target range of 70-140 mg/dL (time in tight range, TITR). We aimed to assess the association between TITR and incident diabetic retinopathy in adults with type 2 diabetes.

Materials and methods: This is a dynamic cohort study conducted at a tertiary hospital. 2518 adults with type 2 diabetes and without diabetic retinopathy at baseline were finally included. TITR was obtained from continuous glucose monitoring data at baseline. Cox proportional hazard regression analysis was performed to assess the relationships of TITR with the risk of incident diabetic retinopathy.

Results: During a mean follow-up period of 5.43 years, 646 patients developed retinopathy. The multivariable-adjusted hazard ratios (HRs) for incident retinopathy across descending TITR quartiles (Q4: >58% [reference], Q3: 38% ~ 57%, Q2: 19% ~ 37%, and Q1: <19%) were 1.00, 1.47 (95%CI 1.16, 1.87), 1.52 (95%CI 1.20, 1.93) and 1.93 (95%CI 1.53, 2.43), respectively. For per 10% decrease in TITR, the risk of diabetic retinopathy was increased by 9% (HR = 1.09, 95%CI 1.06, 1.13) after full adjustment for covariates. In the TIR >70% subgroup, the significant association between TIR, as a continuous variable and the risk of incident retinopathy disappeared, whereas TITR remained significantly associated with the outcome. Similar results were observed in the TIR >80% and TIR >90% subgroups.

Conclusions: TITR is inversely associated with the incidence of diabetic retinopathy in adults with type 2 diabetes. Among adults with well-controlled TIR (70% or higher), TITR may provide added value regarding glucose control.