Diabetes-Prone People at Risk for Alzheimer’s Plaques

People at risk for type 2 diabetes are also more likely to have brain abnormalities associated with Alzheimer’s disease, according to a new study from Japan. The study is the latest evidence of a diabetes-dementia link.

The researchers found that men and women in their 60s with higher-than-average levels of blood sugar (glucose) or insulin—two signs of type 2 diabetes—are between three and six times more likely to have certain protein deposits in their brains a decade or more later, according to the study, which appears in the journal Neurology.

The deposits, known as plaques, don’t always lead to Alzheimer’s disease, but they do raise the risk of the memory-robbing condition.

If future research confirms that high glucose and insulin can in fact cause some cases of Alzheimer’s, it may open the door to preventative drugs that target the insulin system, says William Thies, PhD, chief medical and scientific officer at the Alzheimer’s Association, a nonprofit research and advocacy group.

“That’s ultimately why people are so interested in this relationship,” says Thies, who was not involved in the new research.

Alzheimer’s disease affects as many as 5 million people in the U.S., and the cause is largely unknown (although genes play a role).

About 24 million people in the U.S. have diabetes, and about 90% of those have type 2. Type 2 diabetes is caused by insulin resistance, a condition in which the body loses its sensitivity to the hormone insulin. The result is greater production of insulin—as the body struggles to overcome resistance—and high blood sugar, because the insulin that’s produced can’t move the blood sugar into the liver and muscles.

Obesity and a lack of exercise raise the risk of type 2 diabetes, and several studies have shown that people with type 2 are at increased risk of dementia and faster cognitive decline as they age.

In the study, researchers autopsied the brains of 135 Japanese people from a single town who died between 1998 and 2003. (The average age at death was just under 80.) Ten to 15 years earlier, the researchers had given the study participants a glucose tolerance test, a common test for diabetes. They also measured other health factors such as blood pressure, cholesterol, and body mass index.