Estimated glucose disposal rate is associated with continuous glucose monitoring metrics in type 1 diabetes

Abstract Estimated glucose disposal rate (eGDR) is a composite surrogate of insulin sensitivity in type 1 diabetes (T1D) that incorporates HbA1c, creating potential construct overlap when associations with continuous glucose monitoring (CGM)-derived metrics are examined. In this cross-sectional study of 64 adults with T1D, we evaluated eGDR–CGM associations and the contribution of the HbA1c component, using component-wise analysis as the primary interpretive approach. In conventional models adjusted for age, diabetes duration, and insulin delivery method, higher eGDR was associated with higher time in range (TIR), lower time above range (TAR), lower mean glucose, and lower glucose standard deviation (SD) and coefficient of variation (CV). However, after additional adjustment for HbA1c, eGDR was no longer associated with TIR, TAR, or mean glucose. Nominal associations remained with CV (β=−0.86% points, p = 0.043) and SD (β=−1.85 mg/dL, p = 0.031), but neither survived false-discovery-rate correction. In exploratory HbA1c-independent sensitivity analyses, higher CACTI estimated insulin sensitivity (eIS) was nominally associated with lower CV (β=−1.06% points, 95% CI − 1.97 to − 0.16; p = 0.0217; FDR q = 0.065) and lower SD (β=−2.72 mg/dL, 95% CI − 4.79 to − 0.65; p = 0.0109; q = 0.065); neither association survived FDR correction. Adjustment of the eGDR–SD model for mean glucose attenuated but did not eliminate the association, whereas simultaneous adjustment for HbA1c rendered it non-significant (β=−1.38 mg/dL, 95% CI − 2.79 to 0.02; p = 0.054). No association with TBR was observed (Spearman ρ=−0.056, p = 0.661). TIR > 70% was achieved by 24/64 participants. eGDR showed modest within-sample discrimination (AUC 0.704, 95% CI 0.562–0.829), whereas HbA1c alone had an AUC of 0.865 (95% CI 0.769–0.939). The associations with TIR, TAR, and mean glucose were largely attributable to shared HbA1c. The nominal variability associations did not survive FDR correction and remain exploratory.