The performance of a novel, diabetes-specific cognitive screening tool against the MoCA in older adults with type 2 diabetes

BACKGROUND: Older adults with type 2 diabetes mellitus (T2DM) are at a significantly greater risk of cognitive impairment than those without T2DM. Existing screening tools, such as the Montreal Cognitive Assessment (MoCA), are not tailored to the vascular cognitive profile characteristic of T2DM. To address this gap, we designed the Diabetic Cognitive Assessment Tool (DCAT), a simplified instrument for efficient screening of cognitive impairment in older adults with T2DM, and assessed its performance against the MoCA. The associations of glycaemic control, frailty, depression, education, age, and T2DM duration with cognitive performance were also assessed. METHOD: A cross-sectional study was conducted among 103 adults aged 65 years and older with T2DM attending a tertiary hospital diabetic clinic in Johannesburg, South Africa. Additionally, 55 age- and sex-comparable controls without T2DM were recruited. Cognitive function was assessed using the DCAT and MoCA, whereas frailty and depression were assessed using the FRAIL scale and Geriatric Depression Scale. DCAT performance relative to the MoCA was evaluated using the receiver operating characteristic (ROC) curve analysis and Youden's index identified the optimal cut-off. Associations between clinical and cognitive measures were analysed using Spearman's correlation, and Cohen's d quantified domain-specific effect sizes. RESULTS: The DCAT's area under the curve was 0.81. Using a cut-off score of 13, the DCAT achieved a sensitivity of 78.4% and specificity of 78.7%, with positive and negative predictive values of 89.2%, and 56.9%, respectively. Among participants with T2DM, HbA1c levels correlated negatively with MoCA scores, and depression scores correlated negatively with both DCAT and MoCA scores. In both groups, years of education correlated positively with both cognitive measures. Age and T2DM duration did not correlate significantly with cognitive measures in either group. The executive function and memory domains exhibited large and medium effect sizes, respectively. CONCLUSION: The DCAT demonstrated good discriminative ability in screening for cognitive impairment among older adults with T2DM. Poorer glycaemic control and depressive symptoms were associated with lower cognitive performance, whereas greater educational attainment was associated with better outcomes. The DCAT effectively assesses key cognitive domains, particularly executive function and memory. Further validation in larger, more diverse cohorts is warranted.