Rate of peripheral glucose change during cognitive testing predicts performance in diabetes mellitus.

Background: The reason for cognitive deterioration in diabetes mellitus (DM) remains unknown. One suggestion is that despite elevated glucose levels, patients with DM generally have difficulty utilizing glucose during cognitive tasks. This assumption was tested in the present study.

Methods: Male outpatients with DM (n = 46; age 52-85 years) were administered a series of standard neuropsychological and cognitive tests. In addition to assessing the time to complete the series of tests, peripheral blood glucose levels were measured prior to and following testing.

Results: The rate at which peripheral blood glucose levels changed was examined in relation to cognitive performance. Multiple linear regression analyses revealed significant relationships between the rate of glucose change and performance on tests measuring psychomotor skills, attention, visuoperceptual abilities, sequencing skills, mental flexibility, and planning. Higher rates of decline in peripheral blood glucose levels were associated with better performance on all cognitive measures, except verbal fluency.

Conclusions: During cognitive testing, higher rates of decline in peripheral blood glucose levels may reflect stronger glucose utilization by the brain, thereby facilitating higher levels of cognitive performance. This non-invasive measure may be useful in primary care settings to provide a link between blood glucose changes and cognitive status.