Glucose enhancement of memory in elderly humans: An inverted-U dose-response curve

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

“…However, these findings Riby, 2004) are not consistent with other investigations of the glucose memory facilitation effect in older adults which have found that glucose improves verbal episodic memory performance subsequent to a 50 g glucose dose (Hall et al, 1989;Manning et al, 1990;Manning et al, 1997;Manning et al, 1992;Manning et al, 1998). On this basis, Parsons and Gold (1992) suggest that it may not be the size of the glucose dose per se that determines the effectiveness of glucose administration in facilitating memory performance. More specifically, the blood glucose concentration following the delivery of glucose appears to be the most relevant parameter (blood glucose concentration subsequent to a glucose load is modulated by various factors including, but not limited to, glucoregulatory efficiency and body mass index).…”

“…Table 1 displays the findings of studies which have specifically investigated the influence of oral glucose ingestion in healthy elderly individuals (versus saccharin placebo) on various measures 5 of neurocognitive performance. Verbal episodic memory was the domain of cognitive functioning that was most frequently considered in these studies, with the majority of studies concluding that glucose improves verbal episodic memory performance in healthy elderly individuals (Hall et al, 1989;Manning et al, 1990;Manning et al, 1997;Manning et al, 1992;Manning et al, 1998;Parsons and Gold, 1992;Riby et al, 2004). Glucose was also observed to enhance performance in additional cognitive domains in this age group, including attention , design fluency, verbal fluency and visual memory (Allen et al, 1996).…”

“…However this procedure is not typically used in 7 human studies (c. f. Messier et al, 1998). Based on the results reported by Parsons and Gold (1992), it appears that the most effective blood glucose range for observing enhancement of verbal episodic memory in elderly individuals is approximately 8-10 mmol/L.…”

“…The rationale for theories which implicated glucose as a potential cognitive enhancer in elderly individuals was that ageing is accompanied by neuroendocrine dysregulation , including deficiencies in the regulation of key hormones involved in both memory storage and glucose regulation, such as adrenaline (Gold, 2005;Korol and Gold, 1998). In addition, poor glucose regulation is particularly prevalent in older individuals (Awad et al, 2002;Messier, 2004Messier, , 2005Messier and Gagnon, 1996;Parsons and Gold, 1992). Table 1 displays the findings of studies which have specifically investigated the influence of oral glucose ingestion in healthy elderly individuals (versus saccharin placebo) on various measures 5 of neurocognitive performance.…”

“…In the study by Parsons and Gold (1992), participants presented for testing on four different days, separated by an interval of at least one week. In a counterbalanced order, participants received one of three glucose doses (10 g, 25 g, 50 g) or a saccharin placebo in each of the four test sessions.…”