Impact of Diabetes on Alzheimer's Disease: Concerns Extend Beyond American Health

Studies are suggesting that those with diabetes mellitus tend to get Alzheimer's disease more frequently and possibly even at an earlier age as compared to the general public.
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We all know sugar, especially at higher levels of intake, is bad for our health. We know that it worsens aging of skin, suppresses immune functioning, puts us at higher risk for diabetes and cardiovascular diseases and worsens inflammation in the body.

But, increasingly, we are seeing that the impact of chronic elevated sugar intake and sugar levels in our bloodstream may also lead to neurodegenerative issues to a significant degree. With glucose intolerance and insulin insensitivity, there seems to be a correlation with Alzheimer's as seen in diabetic patients. Studies are suggesting that those with diabetes mellitus tend to get Alzheimer's disease more frequently and possibly even at an earlier age as compared to the general public.

According to Dr. Schubert, a neurobiologist at Salk Institute in La Jolla, Calif., people with type 2 diabetes mellitus are at a 50-100 percent higher risk of developing Alzheimer's disease than non-diabetics. These are astonishing numbers when you think about the number of people in the U.S. who have type 2 diabetes mellitus.

The potential economical, health and social implications of what's to come for the large numbers of Americans who have type 2 diabetes, who are looking at potentially developing Alzheimer's disease, are staggering. According to the Alzheimer's Association, about 5 million Americans already have Alzheimer's disease. And according to the Centers for Disease Control and Prevention, about 8 percent of the entire U.S. population have diabetes, whereas 23 percent of people older than 60 have it. With similarly concerning figures, the National Institute of Diabetes & Digestive & Kidney Diseases reports that about 90-95 percent of those with diabetes have type 2 diabetes mellitus, and that we are increasingly seeing it occur in younger people.

These numbers are very concerning because we are essentially looking at longer periods of exposure to insulin insensitivity and glucose intolerance, because onset is increasingly occurring in younger people. With the hypotheses that insulin plays a strong role in growth and survival of neurons and that elevated blood glucose levels cause damage by forming advanced glycation end products, the overall impact on neuronal and cognitive functioning is dramatically significant.

So, if Americans are developing diabetes at younger ages we may, in fact, develop Alzheimer's at earlier stages in our life, where we would otherwise still have been working and leading active functional lives. With the increasingly earlier onset of diabetes and its potential lead toward earlier onset of Alzheimer's disease, we are essentially looking at a potential significant negative impact on overall American health, economical productivity and social climate.

Even though the medical community has been vigilantly monitoring those with diabetes to make sure that diabetic patients have well-controlled sugar levels, the greater movement should be toward implementation of diabetes prevention programs. Way too often, I am seeing patients who have already developed pre-diabetes or diabetes before they are made to be concerned, whereas the patients who have had years of increasingly elevated trends of fasting sugars are being ignored, as long as the number is below 100.

My recommendation is that we move toward more stringent guidelines, where even the fasting blood glucose levels that are creeping into the mid- to upper-90s should be addressed. Patients who used to have fasting sugars in the 80s, who are now consistently coming up with fasting sugars in the 90s, should have nutritional counseling. Physicians should be urging these patients to make significant changes in their lifestyle, weight and diet such that glucose intolerance stays at bay.

My personal belief is that, even though we know sugar is not good for our health and glucose intolerance is concerning, we are not yet taking the necessary important steps toward being more stringent with our patients at earlier stages of disease development, in regard to their fasting sugar levels that are trending up.

In general, we are waiting for the fasting sugar to hit 100 before we make moves to lower the blood sugar level -- and even then, not all of the patients or physicians become too concerned with pre-diabetes. I see this happening way too often in my clinic, and that concerns me as a physician who practices medicine with the philosophy that I want to "fix the leaky faucet before it overflows" into being a full-blown disease state.

These studies and scientific suggestions of the far-reaching implications of glucose intolerance and insulin insensitivity should hopefully spur us all to put more emphasis on changing our diet and lifestyle, way before we reach that "pre-diabetes" classification, so that we may all keep ourselves and our loved ones as healthy and productive for as long as we can. In doing so, we can hopefully stave off the negative tides of the impact of Alzheimer's disease in increasingly younger and larger population of Americans.


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• Klein WL, et al. Proc. Natl. Acad. Sci. USA 2009, 106, 1971.

• Schubert DR, et al. Neurobiol. Aging. DOI: 10.1016/j.neurobiolaging.2008.02.010.