Peripheral Insulin Resistance Is Unrelated to Cognition in Highly Educated, Cognitively Normal Adults

Abstract Objectives Peripheral insulin resistance (IR) and impaired glucose metabolism increase the risk for cognitive decline. However, data looking at peripheral IR's relationship with cognition in cognitively normal adults is limited. This study aimed to assess the relationship between peripheral IR and tests of executive function, attention, and processing speed in cognitively normal older adults using a novel IR measure. Methods Baseline data from 81 cognitively normal older adults participating in a nutrition intervention study (Nutrition Interventions for Cognitive Enhancement study; NICE study) were analyzed. Fasting blood draws were attained, and peripheral IR was measured using Quest Diagnostics’ Cardio IQ Insulin Resistance Panel (Test Code: 36,509). The NIH Toolbox Cognition Battery was conducted by a trained psychometrician. Executive function was measured by the Flanker Inhibitory Control and Dimensional Change Card Sort tests. The Flanker test also measures attention. Processing Speed was measured by the Pattern Comparison Processing Speed test. We constructed ordinary least squares regression models to assess IR's relationships with the individual cognitive tests, including age, education, and gender as covariates. Statistical analyses were performed using R (v. 3.6.2; R Foundation, Vienna, Austria). Statistical significance was set at p < 0.05. Results Participants were 83% female and had a mean age of 72 ± 4.9 years. The mean IR score was 29.9 ± 29.83. There was no statistically significant relationships with IR and any of the cognitive tests: Flanker Inhibitory Control (β = -0.03, P = 0.12), Dimensional Change Card Sort (β = -0.03, P = 0.16), Pattern Comparison Processing Speed (β = -0.10, P = 0.15). Conclusions There were no statistically significant relationships between IR scores and performance on the different cognitive tests. Although the tests were not significantly correlated with IR scores, directionality of the relationships indicated trend for higher IR being related to poorer scores. Consequently, maintaining insulin sensitivity with healthy lifestyle choices may be important for healthy brain aging. Future analyses with a larger sample size will be more informative for understanding the relationship between IR and various cognitive tests at baseline and over time. Funding Sources National Institutes on Aging.