Effects of prediabetes and type 2 diabetes on cognitive functions.

Background: We aimed to investigate the effect of glycemic impairment in prediabetes on cognitive impairment and the impact of glycemic control on cognitive function in patients with diabetes.

Methods: This age- and sex-matched case-control study included a total of 80 individuals: 20 patients with prediabetes, 20 patients with well-controlled type 2 diabetes mellitus (T2DM) (HbA1C < %7.5), 20 patients with poorly controlled T2DM (HbA1C >% 7.5), and 20 healthy controls.

Results: The poorly controlled T2DM patients performed significantly worse than controls and patients with prediabetes in the verbal memory process test (p = 0.041). In Trail Making Test B, the well-controlled and poorly-controlled groups with diabetes performed significantly worse (p = 0.015) than patients with prediabetes and controls, and in the Wisconsin Card Sorting Test (WCST), all three patient groups performed significantly worse (p = 0.007) than controls.

Conclusions: T2DM causes early brain aging and declines cognitive functions since the prediabetic stage. Poor glycemic control in T2DM patients contributes to cognitive impairments, especially in learning.