The risk of Alzheimer's is high in people with insulin resistance and type 2 diabetes, report researchers in Japan.
The research, published in the American Academy of Neurology, involved 135 people with an average age of 67 from Hisayama, Japan.
The group was tested for blood sugar levels and followed over a period of 10-15 years to detect signs of Alzheimer's.
After the participants died, researchers examined their brains for plaques and tangles, which are physical signs of Alzheimer's -- and found that 65 percent had plaques.
The researchers found that people who gave abnormal results for blood sugar control had an increased risk of developing plaques.
Plaques were found in 72 percent of people with insulin resistance and 62 percent of people with no indication of insulin resistance -- the stage before diabetes when insulin, a hormone in the body, becomes less effective in lowering blood sugar.
"Further studies are needed to determine if insulin resistance is a cause of the development of these plaques," said study author Kensuke Sasaki, with Kyushu University in Fukuoka, Japan.
However, he added, "it's possible that by controlling or preventing diabetes, we might also be helping to prevent Alzheimer's disease."
"Type 2 diabetes and Alzheimer's disease are two epidemics growing at alarming levels around the world," Sasaki said.
"With the rising obesity rates and the fact that obesity is related to the rise in type 2 diabetes, these results are very concerning," he added.
An estimated 37 million people worldwide, including 5.3 million in the United States, live with dementia, with Alzheimer's disease causing the majority of cases, according to the World Health Organization (WHO).