As HbA1c levels rise, cognitive function falls in patients with type 2 diabetes and other cardiovascular risk factors.
Whether lowering glucose levels can improve cognitive function will be addressed in future assessments of the current study group, lead author Dr. Tali Cukierman-Yaffe, from Tel-Aviv University, Israel, and colleagues note.
The current study is not the first to link diabetes with cognitive decline and dementia, the authors explain, but the extent to which hyperglycemia impacts cognition was unclear.
The researchers addressed this topic by analyzing data from the Memory in Diabetes substudy of the Action to Control Cardiovascular Risk in Diabetes (ACCORD-MIND) trial. The study included 2,977 subjects who had HbA1c and fasting glucose levels measured and completed four cognitive function tests: Digit Symbol Substitution Test (DSST), Mini Mental Status Examination (MMSE), Rey Auditory Verbal Learning Test, and Stroop Test.
As glycemic control worsened, so did the scores on all four tests. A 1% increase in HbA1c was associated with a 1.75-point drop in the DSST score (p < 0.0001), 0.20-point fall in the MMSE (p < 0.0001), a 0.11-point decrease in the memory score (p = 0.0142), and worse results on the Stroop Test (p = 0.0094).
By contrast, fasting plasma glucose levels did not correlate with performance on any of the tests, the report shows.
“This cross-sectional analysis illustrates that chronic hyperglycemia appears to be independently associated with cognitive function in individuals with diabetes. It also raises the hypothesis that strategies to lower HbA1c levels or prevent their rise may favorably affect cognitive function,” the research team concludes.
Diabetes Care 2009;32:221-226.