Carbohydrate-induced memory impairment in adults with type 2 diabetes.

OBJECTIVE: Memory impairment is observed in adults with type 2 diabetes. The focus of this study was to determine whether acute carbohydrate consumption contributes to or exacerbates memory dysfunction. RESEARCH DESIGN AND METHODS: The impact of consuming 50 g of rapidly absorbed carbohydrate (one half bagel and white grape juice) at breakfast was examined in 19 adults with type 2 diabetes. Subjects (mean age 63 +/- 9 years, mean BMI 26.1 +/- 4.5 kg/m(2)) were tested, under fed and fasted conditions, on verbal declarative memory using both word list and paragraph recall tests (immediate and delayed [7-min] recall), Trails Test Part B as a measure of general brain function, and mood (subjectively monitoring global vigor and affect).
RESULTS: Under baseline (fasting) conditions, elevated blood HbA(1c) was negatively associated with immediate and delayed paragraph recall performance (R(2) = 0.30; P = 0.024) and higher fasting blood glucose trended toward poorer word list recall (R(2) = 0.09; P = 0.102). Carbohydrate ingestion influenced measures of delayed, but not immediate, recall in a time-dependent fashion (time x food) (word list, P = 0.046; paragraph, P = 0.044) such that delayed recall was improved at 15 min postingestion but was impaired at 30 min. Neither Trails Test scores (P = 0.17) nor mood (affect, P = 0.68 and vigor, P = 0.45) were influenced by food ingestion.
CONCLUSIONS: In adults with type 2 diabetes, poorer glycemic control is associated with lower performance on tests of declarative memory. Acute ingestion of high glycemic index carbohydrate foods further contributes to the underlying memory impairment.