Possible Type 2 Diabetes and Alzheimer's Disease Link

Could type 2 diabetes be a precursor to Alzheimer's disease? A study team out of Japan has just released research results that suggest this possibility.

The scientists recruited 135 older Japanese people with an average age of 67. At the beginning of the study, the participants were given several tests to determine if they had elevated blood glucose levels. Over the next 10 to 15 years, the participants were monitored for typical symptoms of Alzheimer's disease. About 16 percent of them eventually developed Alzheimer's.

After the subjects died, the scientists studied autopsies of their brains and found that about two thirds of them had developed the brain plaques that are typical of Alzheimer's disease. These plaques, known as amyloid plaques, are comprised of protein pieces that lodge and harden between nerve cells. They occurred even in some subjects who did not develop Alzheimer's, suggesting that the markers for the disease may manifest itself years or even decades before symptoms are exhibited. But the real shocker was that the subjects who showed signs of diabetes or insulin resistance at the start of the study were almost six times more likely to have these brain plaques than the other subjects.

While the study's authors could not say for certain that insulin disorders such as diabetes give rise to Alzheimer's disease, they do consider it a possibility. Researchers already know that type 2 diabetes has a detrimental effect on the brain because of its risk of stroke and heart disease. Insulin also can throw certain brain hormones out of balance, which may trigger Alzheimer's. And high blood sugar in general causes inflammation, which can damage brain cells.

Alzheimer's may have several causes, including genetic ones that are independent of diabetes. But scientists have noted that cases of both type 2 diabetes and Alzheimer's have been rising dramatically for the past few years. Since type 2 diabetes may be prevented by eating right and exercising, doing so might possibly help people avoid being diagnosed with Alzheimer's in their lifetimes.

National Institutes of Health, www.nlm.nih.gov