Effect of age and glucoregulation on cognitive performance

Abstract

Type 2 diabetes has been associated with a number of physiological consequences including neuropathy, retinopathy, and incidence of vascular disease. Less is known about the effect on cognition of prediabetes, a period when glucose regulation is abnormal. It is not clear which aspect of impaired glucoregulation is most predictive of cognitive deterioration. In the present experiment, we measured cognitive function in 93 healthy male and female nondiabetic older participants who ranged in age from 55 to 88 years. Various biological measures were obtained including a glucose tolerance test during which glucose and insulin were measured. Participants were evaluated twice, once after drinking a saccharin solution and on another occasion after drinking a glucose solution (50 g). The analysis of the correlations between the biological measures and the results of the cognitive tasks revealed that evoked glucose measures such as peak glucose and glucose at 1 hour were most often correlated with cognitive performance. We observed that progressively worse glucose regulation predicted poorer performance on measures of working memory and executive function-that is, on the Arithmetic, Digit Span Backward, Letter-Number Sequencing, Spatial Span Forward, Spatial Span Backward (trend), and Modified Brown-Peterson tasks. Although, there was no significant facilitative effect of glucose on cognitive performance, it reduced the association between glucose regulation and cognition, apparently by slightly improving performance. These results suggest that cognitive functions may be impaired before glucoregulatory impairment reaches levels consistent with a type 2 diabetes diagnosis.

Glucose enhancement of human memory: A comprehensive research review of the glucose memory facilitation effect

“…Craft et al, 1994;Messier et al, 1997), while the findings of other previous work suggest that glucose enhancement of memory is more likely in poorer glucoregulators (e.g. Kaplan et al, 2000;Messier et al, 2003). This discrepancy between studies is difficult to explain, but may be related to the fact that most studies determine glucoregulatory efficiency groups by performing a median split on some measure of glucose response (such as recovery index).…”

“…However, blood glucose typically remains higher for a longer period in individuals with poor glucose regulation (Donohoe and Benton, 2000). Poor glucoregulation is associated with memory impairment in both aged humans (Convit, 2005;Convit et al, 2003;Dahle et al, 2009;Kaplan et al, 2000;Lamport et al, 2009;Messier, 2005;Messier et al, 1997;Messier et al, 2003;Riby et al, 2004) and rodents (Greenwood and Winocur, 2001;Winocur, 1995). On a related note, brain glucose metabolism (including reduced and slowed capacity for facilitated glucose transport across the blood-brain barrier) is also known to become impaired as a consequence of ageing (Convit, 2005;Korol and Gold, 1998).…”

Glucoregulatory and order effects on verbal episodic memory in healthy adolescents after oral glucose administration

“…A link between glucoregulatory efficiency and cognitive functioning has now been well established (Wenk, 1989;Awad, Gagnon, Desrochers, Tsiakas, & Messier, 2002;Messier, 2005). More specifically, it has been reported that glucose cognitive enhancement effects are most profound in older adults with poorer glucose regulation (Hall, Gonder-Frederick, Chewning, Silvera, & Gold, 1989;Kaplan, Greenwood, Winocur, & Wolever, 2000;Messier, Tsiakas, Gagnon, Desrochers, & Awad, 2003). These findings have also been replicated in younger individuals: young adult males with poor glucose regulation have also been observed to demonstrate superior paragraph recall subsequent to glucose ingestion, relative to ingestion of a saccharin control drink 5 (Craft, Murphy, & Wemstrom, 1994).…”

Impaired Word and Face Recognition in Older Adults with Type 2 Diabetes

“…Problems with glucoregulation in older adults 1 have been shown to adversely impact upon cognitive processing above and beyond normal aging (2,3).…”