Working memory characteristics in T2DM individuals with MMSE-defined cognitive status: a behavioral study

Cognitive decline is frequently reported in individuals with type 2 diabetes mellitus (T2DM), and working memory impairment represents a key feature of diabetes-related cognitive changes. Previous studies have primarily compared T2DM patients with healthy controls and have typically examined only a single working memory domain. The present study aimed to classify T2DM patients based on Mini-Mental State Examination (MMSE) scores and to examine verbal and visuospatial working memory performance under different cognitive load conditions in order to characterize the cross-sectional association between working memory and global cognitive status.

Between November 2023 and June 2024, T2DM patients were recruited from the Department of Endocrinology at the Affiliated Hospital of Yan'an University. Based on MMSE scores, participants were classified into a higher cognitive status group (T2DM-HC, n = 29, MMSE ≥ 27) and a lower cognitive status group (T2DM-LC, n = 25, MMSE 21-26). Working memory performance was assessed using verbal and visuospatial N-back tasks (0-back to 2-back). Reaction time and accuracy were recorded under all task conditions.

Compared with the T2DM-HC group, the T2DM-LC group had a longer duration of diabetes, higher HbA1c levels, and a greater number of comorbidities (all p < 0.05). In both verbal and visuospatial N-back tasks, the T2DM-LC group exhibited significantly longer reaction times (all p < 0.01), and accuracy declined more markedly under high cognitive load (2-back) conditions (all p < 0.001). Partial correlation analyses indicated that MMSE scores were significantly associated only with 2-back accuracy in both verbal and visuospatial conditions (r = 0.461, p < 0.01; r = 0.659, p < 0.001). Hierarchical regression analyses showed that inclusion of verbal 2-back accuracy increased the explained variance by 18.9% (ΔR ² = 0.189), whereas inclusion of visuospatial 2-back accuracy increased the explained variance by 38.6% (ΔR ² = 0.386).

At the cross-sectional level, verbal and visuospatial working memory performance was significantly associated with global cognitive status in patients with T2DM, with group differences most pronounced under high cognitive load conditions. In this sample, visuospatial 2-back performance demonstrated a numerically stronger association with global cognitive status. This finding is exploratory in nature and warrants further investigation in future studies.