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Posted: May 30, 2008

Is Alzheimer's Type 3 Diabetes?

Dementia and Diabetes Linked in Elderly

Research is increasingly linking dementia and diabetes, with their shared infamous reputation for cutting a wide and speedy path through our aging population.

The findings, in fact, are eye-opening: Studies show that people who develop diabetes in midlife or later are at twice the risk for developing dementia.  Diabetes is characterized by chronic high blood sugar, a condition which harms the brain, the resident area of dementia. 

This link may seem to be yet another blow to caregivers whose burdens are already stacked too high.  A closer look, however, shows that this new information may actually make it possible to stave off dementia in their loved one and themselves -- by preventing or controlling diabetes.  

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Diabetes is on the rise due in large part to our country’s obesity epidemic. The number of Americans who have type 2 diabetes has doubled in the last 20 years to more than 20 million cases.   A staggering 41 million people are pre-diabetic, meaning they have blood-sugar levels that are rising toward the diabetic level. 
 
Diabetes is a disease in which the body does not produce or properly use insulin, a hormone that’s needed to convert sugar, starches, and other food into energy needed for daily life.  It is characterized by chronic high blood sugar which harms body and brain. Glucose, a blood sugar, is the brain’s major energy source.  The body regulates glucose by producing insulin released by the pancreas.  High blood sugar occurs when the body doesn’t produce enough insulin, or the organs like the heart, brain, and muscles, don’t respond to the insulin. 

Insulin is as important to the brain as it is to the body.  Insulin modulates cognition and other aspects of normal brain function.  It is needed for learning and memory, and it plays a role in a mechanism necessary for nerve cells to survive and memories to form. 

In type 2 diabetes, the most common form of the disease, the body either does not produce enough insulin or it may be resistant to it.  This is known as insulin resistance, or IR.  IR is characterized by reduced brain insulin levels and insulin activity.  Obesity, type 2 diabetes, and hypertension are strongly associated with IR.  According to a report in the journal Current Alzheimer’s Research in April 2007, IR increases the risk of age-related memory impairment and Alzheimer’s disease.  This risk increases with age, specifically beginning in midlife when the adult body may not respond to normal insulin amounts. 

Diabetes and dementia share several links.  They include risk factors such as midlife obesity and lack of physical activity.  Diabetics and pre-diabetics are also prone to other health problems that can increase the risk of dementia such as stroke, high blood pressure and high cholesterol, all of which are associated with poor mental performance. 

Another shared link is the toxic effect high blood glucose may have on the brain.  Amyloid proteins, which are similar to senile plaques, form when blood sugar in the brain is too high.  Amyloid build-up kills brain cells.  This is the same protein found in the brain of Alzheimer’s patients and in the pancreas of diabetics, causing some researchers to refer to Alzheimer’s disease as type 3 diabetes.      

Insulin resistance represents yet another link between the two diseases because it leads to cognitive decline similar to that seen in Alzheimer’s patients.  A person with Alzheimer’s disease not only has dysfunctional learning and memory loss, but also a decrease in new brain cell formation and the repair of damaged cells.  Insulin increases inflammation in the brain, as well, contributing to Alzheimer’s. 

The April 9, 2008, issue of the medical journal Neurology published the results of a Swedish study of 2,300 Swedish men who were followed for 32 years after being glucose tested for diabetes at the age of 50.  In all, 102 were diagnosed with Alzheimer’s, 57 with vascular dementia, and 235 with other types of dementia or other cognitive impairment.  The men with low insulin levels at age 50 were nearly one-and-a-half times more likely than those without insulin problems to develop Alzheimer’s despite blood pressure, cholesterol, body mass index or education. 

Says the study author, Elina Ronnemaa of Uppsala University, "Our results suggest a link between insulin problems and the origins of Alzheimer's disease and emphasize the importance of insulin in normal brain function.  It's possible that insulin problems damage blood vessels in the brain, which leads to memory problems and Alzheimer's disease, but more research is needed to identify the exact mechanisms."

Preventing or controlling type 2 diabetes may be a way to prevent Alzheimer’s and other dementia.  Too much fatty tissue reduces the efficiency of insulin in the body, which can alter the activity and health of brain cells.  Researchers at the Johns Hopkins Bloomberg School of Public Health have found a consistent connection between obesity and dementia after an analysis of 20 years of studies beginning in 1995.  They concluded that obesity increases the risk of dementia in general by 42%, Alzheimer’s by 80% and vascular dementia by 73%.  There was no added risk in people who were normal or overweight. 

Dr. Youfa Wang, senior author of the study, said, “Preventing or treating obesity at a younger age could play a major role in reducing the number of dementia patients and those with other commonly associated illnesses such as Alzheimer’s disease by up to 20% in the United States.” 

Diabetes is both preventable and controllable.  The American Diabetes Association advises screening beginning at age 45, or sooner if you are overweight and exhibit another risk factor such as having an immediate relative with diabetes, previous gestational diabetes, or if you have hypertension, dyslipidema, or are an ethnicity other than Caucasian.  Be aware that many people show no symptoms of the disease, and diabetes is often not discovered until a screening.  Symptoms that may appear are frequent urination and thirst, fatigue and weight loss, extreme hunger, irritability, and blurred vision.     

Though high blood sugar may mean an increased risk of dementia, pre-diabetes and diabetes can be prevented, delayed, and controlled.  It’s proof of the body-mind connection that says your brain is only as healthy as your body. 

Think of the link between diabetes and dementia as an added motivation to make healthy lifestyle choices, like eating right and exercising that are beneficial to both body and mind.  Living dementia-free for as long as possible is worth it.

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Lori Zanteson is a California-based freelance writer. She specializes in topics related to families and can be reached at lorizanteson@verizon.net.

RESOURCES:
Medicare Diabetes Information
CDC Diabetes Public Health Resource
National Diabetes Information Clearinghouse
American Diabetes Association
National Diabetes Education Program

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