Age-Related Cognitive Decline May Be Linked to High Blood Sugar Levels

[December 2008] Rising blood glucose levels have been identified by scientists as a possible contributing factor in age-related cognitive decline.  

A recent study published in the Annals of Neurology establishes that rising blood sugar levels, a normal part of aging, affect a part of the brain called the hippocampus. This area of the brain is critical to learning, memory, and other cognitive functions.  

Maintaining Optimal Blood Sugar Levels  

Senior study author Dr. Scott Small, an associate professor of neurology at the Taub Institute for Research on Alzheimer's Disease and the Aging Brain at Columbia University Medical Center in New York City states, "This would suggest that anything to improve regulation of blood glucose would potentially be a way to ameliorate age-related memory decline".

The findings may also help explain why people who exercise do not have as many cognitive problems as they age. The implication is that exercising helps to stabilize blood glucose levels and helps maintain cognitive function.

Exercise and Its Impact on Blood Glucose 

Rising blood sugar levels may be a risk factor for mental decline, but it is good news that this problem is usually  amenable to change. Physical exercise might just be an uncomplicated, yet effective antidote.

"We had previously shown that physical exercise strengthens a part of the brain involved with aging but, at the time, we didn't know why physical exercise would have this selective benefit," Dr. Small says. "Now we have a proposed mechanism. We think it's because subjects who exercised had better glucose handling."

New Insight On Specific Brain Region  

It is well known that damage to the hippocampus is evident with Alzheimer's disease, and there has been some suggestion that this region of the brain is also affected by normal aging. The researchers used magnetic resonance imaging (MRI) to record the functioning of the hippocampus in 240 healthy older people with an average age close to 80. Sixty of the participants had type 2 diabetes, while 74 had brain "infarcts" - some damage to brain tissue.

The studies indicate that diabetes and infarcts are each linked with separate areas of the hippocampus, suggesting that different mechanisms are at work in each disorder. These findings were subsequently confirmed in animal studies. 

"The paper identifies an etiology [cause] for normal age-related memory decline," Small explains. "Elevations in blood glucose levels differentially target the dentate gyrus part of the hippocampus implicated in aging and, as we age, we develop a slight but gradually worsening difficulty in handling blood sugar levels."  

Further Research Expected

At this time, expert opinion has not reached a final consensus. Some experts such as Dr. Bryan Freilich, a clinical neuropsychologist at Montefiore Medical Center in New York City encourages continued research. He says, "In my opinion, that's an interesting hypothesis and needs to be studied - that exercise helps improve cognitive functioning through that mechanism, but I think there are other mechanisms as well".

This early study may provide useful clinical information. Dr. Mark Mapstone, an associate professor of neurology at the University of Rochester Medical Center in New York, says: "If these findings are replicated and confirmed, I think the implications could be very important, specifically, that maintaining optimal blood sugar levels throughout aging is a feasible way to [slow or prevent] cognitive decline. It goes beyond diabetes to look at people who don't have diabetes. The implication is even if you don't have a clinical condition of diabetes, that you can still do something about cognitive aging."

Always consult your physician for more information.