Associations between Markers of Glucose and Insulin Function and Cognitive Function in Healthy African American Elders

Abstract

Background: Glucose and insulin are important moderators of cognitive function. African Americans have poorer glycemic control across the glycemic spectrum and are at increased risk for type 2 diabetes and poor cognitive health. It is unclear which glucoregulatory markers predict cognitive function in this at-risk population. The purpose of this study was to examine the association between cognitive function and common markers of glucoregulation in non-diabetic African Americans elders.

Methods: Thirty-four, community-dwelling African Americans, aged 50-75 years completed cognitive testing and blood collection as part of a health screening assessment. Cognitive outcomes were composite scores derived from neuropsychological tests of executive function and verbal memory. Linear regression was used to examine relationships between cognitive composite scores and fasting blood levels of glucose, insulin, and hemoglobin A1C, with adjustments for age, education, body mass index, and antihypertensive medication use.

Results: Fasting plasma glucose was negatively associated with executive function (β=-0.41, p=0.03). There was a trend of an association between fasting plasma glucose and verbal memory (β=-0.34, p=0.06). Fasting insulin and hemoglobin A1c were not associated with cognitive function.

Conclusion: High non-diabetic fasting glucose levels were associated with poorer executive function and verbal memory. These results provide preliminary support for proactive glucose control in older African Americans even before glycemic criteria for type 2 diabetes are met. Our findings suggests that high-normal FPG levels may represent an early red-flag to signify increased risk of cognitive impairment or decline.

Keywords: African Americans; Executive function; Glucose; Memory; Type 2 diabetes.

Figures

Figure 1

Unadjusted correlation between fasting glucose (mg/dL) and executive function composite score (r=−0.35, p=0.05). The composite score was constructed by summing z-scores for Trails B of the Trail Making Test, number correct on Digit-Symbol, Digit Span Backwards, and Word Fluency.

Figure 2

Unadjusted correlation between fasting glucose (mg/dL) and verbal memory composite score (r=−0.30, p=0.07). The composite score was constructed by summing z-scores for the California Verbal Learning Test (CVLT) and Logical Memory of the Wechsler Memory Scale (WMS-III).