Factors associated with the dawn phenomenon in adults with type 1 diabetes: a probabilistic continuous glucose monitoring analysis

Abstract

The dawn phenomenon (DP), an early-morning rise in glucose levels, remains a challenge in the management of type 1 diabetes mellitus (T1DM). This study aimed to identify factors associated with DP frequency in adults with T1DM. We analyzed data from 265 adults with T1DM enrolled in the FGM-Japan study. Continuous glucose monitoring (CGM) data obtained using the FreeStyle Libre system for approximately 90 days were analyzed. DP was defined as a glucose rise ≥20 mg/dL from the nocturnal nadir without preceding nocturnal hypoglycemia. DP probability was estimated using a probabilistic computation framework incorporating CGM sensor error. Multivariable linear regression and k-means clustering were used to identify factors and phenotypic patterns associated with DP. Sensitivity analyses were performed using alternative DP thresholds (≥10 mg/dL and ≥30 mg/dL). The mean DP frequency was 0.305 (95% CI, 0.288–0.323). Three clusters with increasing DP frequency were identified, characterized by male predominance, shorter diabetes duration, higher HbA1c levels, and greater post-breakfast glucose excursions. Continuous subcutaneous insulin infusion use was lowest in the highest-DP cluster and was associated with lower DP frequency. Male sex, higher HbA1c, and higher γ-glutamyl transferase levels were independently associated with greater DP. DP in adults with T1DM is associated with glycemic control and liver-related metabolic markers, particularly γ-glutamyl transferase. The trial was registered with the UMIN Clinical Trials Registry (UMIN-CTR; registration number UMIN000039376).