Researchers have found that people with diabetes may face a significantly higher risk for developing Alzheimer's disease, based on the impact uncontrolled blood sugar can have on the brain.

Abnormally high levels of blood sugar may have a negative effect on cognition and brain condition, years before any dementia symptoms become apparent, according to two recent studies. 

A study using mice found that raising the rodents' blood sugar to abnormally high levels triggered increased production of amyloid beta in the brain — a protein considered a significant factor in the development of Alzheimer's disease, said the study scientists at Washington University in St. Louis.

The buildup of plaque from these proteins is thought to be one of the first in several steps bringing on a complex set of changes in the brain tied to Alzheimer's.

"Our results suggest that diabetes, or other conditions that make it hard to control blood sugar levels, can have harmful effects on brain function and exacerbate neurological conditions such as Alzheimer's disease," said study lead author Shannon Macauley, a postdoctoral research scholar. "The link we've discovered could lead us to future treatment targets that reduce these effects."

In another study, which was done at the University of Pittsburgh, middle-aged people with Type 1 diabetes displayed more brain lesions, and had slower cognitive functions, that people not suffering from diabetes.

The Pittsburgh researchers, reporting their results in the journal Neurology, said they were somewhat surprised at their findings because of the age of the participants — who were at average 50 years old.

It suggests that a negative impact on the brain from uncontrolled blood sugar can exist for years or even decades before the appearance of any symptoms of dementia, said lead study researcher Caterina Rosano.

"The clinical impact is huge over time," said Rosano, associate professor of epidemiology at the university's Graduate School of Public Health. "These abnormalities will impact the speed with which your brain works, and how quickly information travels from one part of your brain to another."

Some experts however emphasized that as important as these studies are, there are many other risk factors for dementia, including genetics and age. They added that most people suffering from diabetes will not develop Alzheimer's and will have lives that are fully functional.

"If we prematurely equate diabetes with a condition as severe as dementia or Alzheimer's, we'd be doing a great disservice to the 29 million people in this country who hold complex positions and fulfill complex job requirements," said Samuel Dagogo-Jack, a diabetes specialist at the University of Tennessee Health Science Center.