Relationships between cerebral structure and cognitive function in African Americans with type 2 diabetes

Background: Relationships between cognitive function and brain structure remain poorly defined in African Americans with type 2 diabetes. Methods: Cognitive testing and cerebral magnetic resonance imaging in African Americans from the Diabetes Heart Study Memory IN Diabetes (n = 480) and Action to Control Cardiovascular Risk in Diabetes MIND (n = 104) studies were examined for associations. Cerebral gray matter volume (GMV), white matter volume (WMV) and white matter lesion volume (WMLV) and cognitive performance (Mini-mental State Exam [MMSE and 3MSE], Digit Symbol Coding (DSC), Stroop test, and Rey Auditory Verbal Learning Test) were recorded. Multivariable models adjusted for age, sex, BMI, scanner, intracranial volume, education, diabetes duration, HbA1c, LDL-cholesterol, smoking, hypertension and cardiovascular disease assessed associations between cognitive tests and brain volumes by study and meta-analysis. Results: Mean(SD) participant age was 60.1(7.9) years, diabetes duration 12.1(7.7) years, and HbA1c 8.3(1.7)%. In the fully-adjusted meta-analysis, lower GMV associated with poorer global performance on MMSE/3MSE (β̂ = 7.1 × 10 ⁻³ , SE 2.4 × 10 ⁻³ , p = 3.6 × 10 ⁻³ ), higher WMLV associated with poorer performance on DSC (β̂ = −3 × 10 ⁻² , SE 6.4 × 10 ⁻³ , p = 5.2 × 10 ⁻⁵ ) and higher WMV associated with poorer MMSE/3MSE performance (β̂ = −7.1 × 10 ⁻³ , SE = 2.4 × 10 ⁻³ , p = 3.6 × 10 ⁻³ ). Conclusions: In African Americans with diabetes, smaller GMV and increased WMLV associated with poorer performance on tests of global cognitive and executive function. These data suggest that WML burden and gray matter atrophy associate with cognitive performance independent of diabetes-related factors in this population.