Investigating the Spectrum of Normoglycemia: Time in Glycemic Ranges and Their Association with Metabolic Outcomes in Individuals Without Diabetes

OBJECTIVE To characterize the distribution of time in tight and broader glycemic ranges in adults without diabetes, and to examine cross-sectional and longitudinal associations with metabolic health. RESEARCH DESIGN AND METHODS We analyzed continuous glucose monitoring data from 8,687 adults (40–70 years, 54% women) in the Human Phenotype Project, each contributing 1,149 ± 279 glucose readings from FreeStyle Libre Pro sensors. Age- and sex-adjusted correlations linked time-in-range metrics with 45 clinical phenotypes encompassing adiposity, vascular and liver markers, sleep indices, and nutrition. Cox models tested associations of time above glycemic thresholds with incident metabolic disease over 2.6 ± 1.3 years. RESULTS Participants spent a median 93.0% (IQR 91.8–98.2%) of CGM time within 70–140 mg/dL and 95.2% (IQR 95.1–99.8%) within 70–180 mg/dL. Time below 140 mg/dL and 180 mg/dL were 97.7% (IQR 97.6-97.8%) and 99.9% (IQR 99.9-99.9%) respectively. Lower time