Individuals in the prediabetes stage exhibit reduced hippocampal tail volume and executive dysfunction

High glucose levels are associated with cognitive impairment and total hippocampal volume reductions. However, the effects of the blood glucose level on hippocampal subfield volumes remain unclear, especially in the prediabetes stage.

Sixty participants were enrolled in this cross-sectional study and were divided into the nondiabetes, prediabetes, and diabetes groups according to their medical history and A1c level. A full battery of neuropsychological tests was used to assess the global cognition, executive function, attention, verbal fluency, working memory, immediate memory, and delayed memory. FreeSurfer 6.0 was used for the hippocampus parcellation. Hippocampal subfield volumes were adjusted by intracranial volume. Analyses of covariance, multiple linear regression, and partial correlation analysis were used to explore the relationship between A1c level, cognitive function, and hippocampal subfields volume, in which age, sex, education years, body mass index, history of hypertension, level of cholesterol, and the presence of ApoE4-positive status were adjusted.

Significant differences in the total left hippocampal volume (p = 0.046) and left hippocampal tail volume (p = 0.014) were noted among three groups. Significant correlation was identified between the A1c level and the volume of left hippocampal tail (r = -0.334, p = 0.009) after adjusting all the covariants. Increased A1c level was significantly associated with executive dysfunction, as assessed by trail making test B (R = 0.503, p = 0.0016) and Stroop test C (R = 0.506, p = 0.001).

Our results support that the left hippocampal tail volume may be served as an early marker of diabetes-related brain damage, associated with executive dysfunction. Clinicians should pay closer attention to adults in the prediabetes stage to prevent later cognitive impairment.