Relationship between key continuous glucose monitoring-derived metrics and specific cognitive domains in patients with type 2 diabetes mellitus

Abstract

Abstract Objective Continuous glucose monitoring (CGM)-derived time in range (TIR) is closely associated with micro- and macro-vascular complications in type 2 diabetes mellitus (T2DM). This study was performed to investigate the relationship between key CGM metrics and specific cognitive domains in patients with T2DM. Methods A total of 96 outpatients with T2DM were recruited in this study. A battery of neuropsychological tests was performed to evaluate cognitive function, including memory, executive functioning, visuospatial ability, attention, and language. Participants wore a blinded flash glucose monitor (FGM) for 72 h. The key FGM metrics were calculated, including TIR, time below range (TBR), and time above range (TAR). Furthermore, the glycemia risk index (GRI) was also calculated by the GRI formula. Binary logistic regression was used to assess risk factors for TBR, and we further analyzed the associations between neuropsychological test results and TBR/TAR/TIR/GRI with multiple linear regressions. Results A total of 45.8% of patients with T2DM had hypoglycemia (TBR < 3.9) measured by FGM. The Spearman analysis results revealed that a higher TBR < 3.9 was correlated with worse performance on trail making test A (TMTA), clock drawing test (CDT) and cued recall scores (P < 0.05). The logistic regression analysis results revealed that TMTA (OR = 1.010, P = 0.036) and CDT (OR = 0.429, P = 0.016) scores were independent factors influencing the occurrence of TBR < 3.9. Multiple linear regressions revealed that TBR < 3.9 (β = -0.214, P = 0.033), TAR > 13.9 (β = -0.216, P = 0.030) and TAR 10.1–13.9 (β = 0.206, P = 0.042) were significantly correlated with cued recall scores after adjusting for confounding factors. TIR and GRI had no correlation with neuropsychological test results (P > 0.05). Conclusion A higher TBR < 3.9 and TAR > 13.9 were associated with worse cognitive functions (memory, visuospatial ability, and executive functioning). A higher TAR of 10.1–13.9 was associated with better memory performance. For patients with T2DM, glycemic targets can be relaxed to 10.1–13.9 mmol/L, which may slow the decline in cognitive function.