A Link Between Diabetes and Alzheimer’s?

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Two of the most high profile illnesses in North America may now be linked: Alzheimer’s disease and diabetes.

Alzheimer’s is the most common form of dementia. Dementia is a general term for the loss of memory and other intellectual abilities serious enough to interfere with daily life. Although there are many types of dementia, Alzheimer’s disease accounts for 50% to 70% of all dementia cases. Other types of dementia include vascular dementia, mixed dementia, dementia with Lewy bodies, and fronto-temporal dementia. There is no tried-and-true cure for Alzheimer’s.

Diabetes, of course, is a condition in which the body does not produce or cannot properly use insulin. Insulin is important because it controls the amount of glucose (or sugar) in your blood. It also controls the rate at which glucose is absorbed into your cells. Your cells need glucose to produce energy. And, just as importantly, your brain relies on insulin as its only source of food. In order for your brain to function normally, your insulin levels must be maintained at a minimum level.

When you eat a meal, your blood sugar normally rises. This rise triggers a release of insulin from cells in the pancreas. In effect, the insulin opens up the entranceways to your cells which allows glucose to enter them. Once glucose has entered your cells, your blood sugar falls back to normal. The release of insulin slowly tapers off until the next time you eat some protein or carbohydrates. Your blood sugar levels vary every hour of your life — even if you do not have diabetes.

So what’s the link between the two, other than the fact that the brain requires insulin to work properly? Japanese researchers say that having insulin resistance or type 2 diabetes raises your risk of developing the brain plaques associated with Alzheimer’s disease.

The research team found that people with the highest levels of fasting insulin had nearly six times the odds of having plaque deposits between nerves in the brain, compared to people with the lowest levels of fasting insulin.

Those with the highest scores on a measure of insulin resistance (where cells become less able to use insulin effectively) had about five times the odds of having brain plaques vs. those with the lowest scores on the insulin-resistance test, the study also found.

The research team then performed a separate analysis to see if the presence of a gene long associated with Alzheimer’s disease would have an effect on diabetes risk factors and the development of plaques. According to the researchers, it did: those with the gene have the strongest association between high blood sugar levels, insulin resistance and fasting insulin levels, and the development of plaques.

The message seems clear: if you have diabetes, keep it under control. Better yet, if you don’t have it, avoid the condition altogether with regular physical activity and weight maintenance. Preventing or controlling diabetes is good for all kinds of reasons, including reducing your risk for developing Alzheimer’s.