The association between continuous glucose monitoring metrics and mild cognitive impairment in chinese patients with type 2 diabetes mellitus complicated by white matter hyperintensities: a single-center cross-sectional study

Type 2 diabetes mellitus (T2DM) complicated by white matter hyperintensities (WMH) represents a high-risk population for cognitive decline. However, the association between continuous glucose monitoring (CGM) metrics and mild cognitive impairment (MCI) in this specific population remains inadequately explored. This study aimed to evaluate the associations between hemoglobin A1c (HbA1c), CGM metrics and MCI in patients with T2DM and WMH, and to identify potential threshold effects and subgroup differences. This single-center cross-sectional study enrolled 1068 hospitalized patients with T2DM and WMH from January 2020 to December 2025. Cognitive function was assessed using the Montreal Cognitive Assessment (MoCA), with MCI defined as a score of 18–25. Glycemic metrics included HbA1c and CGM-derived parameters, namely mean amplitude of glycemic excursions (MAGE), coefficient of variation (CV), time in range (TIR), time above range (TAR), time below range (TBR), and mean of daily differences (MODD). Multivariable logistic regression, restricted cubic splines, threshold effects analysis, ROC curves, and subgroup interaction tests were performed. Among 1068 patients (396 MCI, 672 non-MCI), MCI patients were older, had fewer years of education, more severe WMH, longer diabetes duration, and higher HbA1c (all P < 0.05). After multivariable adjustment, higher HbA1c (OR = 1.48), MAGE (OR = 3.1), CV (OR = 1.013), TBR (OR = 1.26), and lower TIR (OR = 0.92) were independently associated with MCI (all P < 0.05). MAGE showed the best discriminatory performance (AUC = 0.713). Nonlinear associations and significant threshold effects were identified: MCI risk increased significantly when MAGE ≥ 3.95 mmol/L (OR = 6.23) or HbA1c ≥ 7.86% (OR = 2.94), and decreased when TIR ≥ 65.0% (OR = 0.94). Subgroup analyses revealed effect modifications by alcohol consumption for CV and TIR, and by BMI for TBR. Additionally, MODD and TAR after full adjustment showed no independent associations. In this cross‑sectional study of patients with T2DM and WMH, higher MAGE, HbA1c, CV, and TBR, as well as lower TIR, were independently associated with MCI, with MAGE showing the best discriminative ability. Furthermore, the risk of MCI increased substantially when MAGE ≥ 3.95 mmol/L or HbA1c ≥ 7.86%, and decreased when TIR ≥ 65.0%. These above association warrant further validation in prospective studies before being considered as potential targets for cognitive preservation.