A study published online in Neurology on October 23, 2013 sheds light on the possible mechanisms of dementia in persons with elevated blood glucose but without diabetes as discussed in the previous post. The hippocampus, located in the inner aspect of both temporal lobes, is the key brain structure for memory consolidation and storage.
The researchers “aimed to elucidate whether higher glycosylated hemoglobin (HbA1c) and glucose levels exert a negative impact on memory performance and hippocampal volume and microstructure in a cohort of healthy, older, nondiabetic individuals without dementia.”
Learning tests, blood levels of HbA1c, glucose, and insulin, and advanced (3-tesla) MRI scans were performed on 141 persons (72 women & 69 men) with an average age of 63. Those with lower glucose and HbA1c levels had better learning and memory and a healthier hippocampi:
“Lower HbA1c and glucose levels were significantly associated with better scores in delayed recall, learning ability, and memory consolidation. …Moreover, mediation analyses indicated that beneficial effects of lower HbA1c on memory are in part mediated by hippocampal volume and microstructure.”
The authors concluded:
“Our results indicate that even in the absence of manifest type 2 diabetes mellitus or impaired glucose tolerance, chronically higher blood glucose levels exert a negative influence on cognition, possibly mediated by structural changes in learning-relevant brain areas. Therefore, strategies aimed at lowering glucose levels even in the normal range may beneficially influence cognition in the older population, a hypothesis to be examined in future interventional trials.”