The effect of glucose regulation on cognitive functioning in a healthy sample of older adults

Abstract

Type II diabetes and impaired glucose tolerance (IGT) are both associated with cognitive impairment and an increased risk of dementia, and normal aging has been shown to be accompanied by abnormalities in glucose regulation. The present study was conducted to determine if variations in cognitive performance would be observed as a function of glucose regulation in a healthy elderly population. Thus, cognitive functioning was measured in 93 healthy male and female older participants who ranged in age from 55 to 88. Participants had a glucose tolerance tests from which several biological indices were obtained including various glucose and insulin measures, and were separated into better and poorer glucoregulatory groups on the basis of these indices. Participants underwent two cognitive testing sessions, one after drinking a saccharin solution and another after drinking a glucose solution (50g). Participants with worse glucose regulation performed worse on measures of working memory, executive function, and processing speed compared to participants with better glucose regulation. Additionally, older participants with worse glucose regulation obtained the lowest scores on the majority of cognitive measures compared with younger participants and those with better regulation. A significant enhancement of cognitive performance by glucose was not clearly observed. The results suggest that cognitive functioning may be compromised before glucoregulatory impairment reaches levels consistent with IGT or Type II diabetes.