94-OR: CGM Metrics, HbA1c, and Retinopathy Are Differentially Associated by Disease Duration in Long-Duration Type 1 Diabetes

Abstract

Continuous glucose monitor (CGM) -derived metrics provide measures of glycemic variability that are not captured with the use of HbA1c alone. However, they have not been evaluated in long-duration type 1 diabetes (T1D) subjects, in whom the greater risk of glycemic excursions and comorbidities highlight the need for other glycemic markers apart from HbA1c. Among the Joslin “Medalists” with T1D≥50 years, a single consecutive 14-day block of CGM data was remotely obtained from a subset of CGM users (n=64) after a period of routine activities. Using linear regression, mean historical HbA1c associated with mean glucose (β= 17.54, p<0.0001) , glucose management indicator (GMI; β= 0.42, p<0.0001) , and time above range (TAR) >250 mg/dL (β= 3.31, p=0.0003) ; and inversely with time in range (TIR) 70-180 mg/dL (β= -8.08, p=0.0003) and time below range (TBR) <70 mg/dL (β= -2.11, p=0.0006) . While no associations were found between CGM metrics and complications in the overall subset, tertile analysis by T1D duration (tertile 1, 51-61 years; tertile 2, 62-69 years; tertile 3, 70-85 years) revealed that T1D duration modified the effect of CGM metrics on proliferative retinopathy (PDR) even after adjusting for HbA1c (p for interaction <0.05) . In subjects with the longest T1D duration (tertile 3) , PDR associated with mean glucose (β= 26.92, p=0.02) , GMI (β= 0.64, p=0.02) , and TAR (β= 6.81, p=0.03) ; and inversely with TIR (β= -12.57, p=0.04) . Tertile analysis of HbA1c and complications in the overall Medalist cohort (n=952) showed that HbA1c associated with PDR in tertile 1 (p=0.03) . Our results suggest that while HbA1c and CGM metrics are closely linked in long-duration T1D subjects, they may provide differential contributions to the temporal onset of microvascular complications, independent of each other. Additionally, as development to PDR has been demonstrated to stabilize in Medalists with the longest T1D duration, favorable values of CGM metrics may contribute to this protection. Disclosure M.Yu: None. T.Boumenna: None. J.Gauthier: None. R.Tham: None. W.Fickweiler: None. J.Sun: Consultant; American Diabetes Association, American Medical Association, Research Support; Adaptive Sensory Technology, Boehringer Ingelheim International GmbH, Genentech, Inc., Jaeb Center for Health Research, Janssen Pharmaceuticals, Inc., Novartis Pharmaceuticals Corporation, Novo Nordisk, Optovue, Incorporated, Physical Sciences, Inc, Roche Pharmaceuticals. H.Shah: None. G.L.King: Advisory Panel; Medtronic, Research Support; Janssen Pharmaceuticals, Inc. Funding American Diabetes Association (9-18-CVD1-005) ; Mary K. Iacocca Family Foundation, Thomas Beatson Jr. Foundation, National Eye Institute (R01EY026080-01)