Mildly Elevated Glucose Impairs Cognition

This New York Times article reinforces the case for blood sugar control for improved cognition.

Blood Sugar Control Linked to Memory Decline, Study Says


Published: December 31, 2008

Spikes in blood sugar can take a toll on memory by affecting the dentate gyrus, an area of the brain within the hippocampus that helps form memories, a new study reports.

High glucose seemed to affect the dentate gyrus, part of the hippocampus

Researchers said the effects can be seen even when levels of blood sugar, or glucose, are only moderately elevated, a finding that may help explain normal age-related cognitive decline, since glucose regulation worsens with age.

 “If we conclude this is underlying normal age-related cognitive decline, then it affects all of us,” said lead investigator Dr. Scott Small, associate professor of neurology at Columbia University Medical Center. “The ability to regulate glucose starts deteriorating by the third or fourth decade of life,” he added.

“But the elevations in blood glucose seen in the new study are more subtle and would not be considered a disease state,” Dr. Small said.

“It’s part of the normal process of aging, much like wrinkling of skin,” he said. “It happens to all of us inexorably, and it worsens progressively across the life span.”

This article reports on the following research paper:

The brain in the age of old: the hippocampal formation is targeted differentially by diseases of late life.

Wu W, Brickman AM, Luchsinger J, Ferrazzano P, Pichiule P, Yoshita M, Brown T, DeCarli C, Barnes CA, Mayeux R, Vannucci SJ, Small SA.

Taub Institute for Research on Alzheimer’s Disease and the Aging Brain, Columbia University College of Physicians and Surgeons, New York, NY, USA

Annals of Neurology. 2008 Dec;64(6):698-706.

A relevant excerpt from the full paper:

Showing that blood glucose selectively targets the dentate gyrus is not only our most conclusive finding, but it is the one most important for ‘normal’ aging—i.e., hippocampal dysfunction that occurs in the absence of disease states, such as AD, infarcts, and diabetes. Indeed, cognitive studies have established that normal age-related hippocampal dysfunction begins quite early, typically during the 4th decade of life, before the onset of age-related diseases. Furthermore, age-related hippocampal dysfunction occurs in all non-human mammals, who do not typically develop AD, stroke, or diabetes. Consistent with this, our cross-species findings document that the detrimental affects of glucose on the hippocampus occurs independent of AD and infarcts, and our monkey findings in particular suggest that it occurs independent of overt diabetes.

Beyond the obvious conclusion that preventing late-life disease would benefit the aging hippocampal formation, our findings suggest that maintaining glucose control, even in the absence of disease, should be strongly recommended to preserve cognitive health. More specifically, our findings predict that any intervention that causes a decrease in blood glucose should increase dentate gyrus function and would therefore be cognitively beneficial. In fact, separate studies examining the effects of physical exercise support this prediction. Imaging studies in humans and mice have documented that among all hippocampal subregions physical exercise causes a differential improvement in dentate gyrus function. By improving glucose metabolism, physical exercise also reduces blood glucose. It is possible, therefore, that the cognitive enhancing effects of physical exercise are mediated by the beneficial effect of lower glucose on the dentate gyrus. Whether through physical exercise or other behavioral or pharmacological interventions, our results suggest that improving glucose metabolism is a clinically tractable approach for ameliorating the cognitive slide that occurs in all of us as we age.

Read the full paper.

The researchers suggest exercise as a way of lowering glucose levels, but in our opinion exercise should not be the be all and end all for maintaining healthy glucose. Nor is high glucose an inevitable disease of aging. Great glucose control is being achieved by members of all ages. Users of the CR Way to Great Glucose Control rely on food selections, meal timing, and tease meals to jump start insulin production – examples of the many proven techniques to lower glucose.

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