Abstract
OBJECTIVE: Estimated time in range (eTIR) obtained from DCCT glucose profiles (pre- and postprandial and bedtime) was recently reported to be associated with microvascular outcomes and was recommended as a clinical trial outcome, but without consideration of HbA1c. RESEARCH DESIGN AND METHODS: The associations of eTIR with diabetic retinopathy and microalbuminuria were assessed without and with adjustment for HbA1c and baseline covariates. RESULTS: Adjusted for HbA1c and covariates, eTIR was marginally significantly associated with retinopathy in the full cohort (hazard ratio [HR] 1.12 per 10% lower eTIR [95% CI 1.0, 1.26], P = 0.042). Conversely, HbA1c was significantly associated with both outcomes (HR ≥1.19 per 0.5% higher HbA1c, P ≤ 0.0002) in five of six adjusted analyses. CONCLUSIONS: The association of eTIR with complications is largely explained by its correlation with HbA1c. HbA1c, not eTIR or continuous glucose monitoring TIR, remains the preferred outcome in clinical studies of type 1 diabetes complications.