According to Dr. Barb Bendlin, lead author, assistant professor of medicine (geriatrics) at UW, and researcher for the Wisconsin Alzheimer’s Disease Research Center, the findings showed high levels of insulin resistance in the brains of study participants and a reduced uptake of glucose.
The research involved 150 members in the Wisconsin Registry for Alzheimer’s Prevention (WRAP) over a two year period. People with a history of Alzheimer’s disease in their families have assisted in research by participating in WRAP to help determine the causes and treatments for the disease.
Bendlin, whose findings will be published in the journal Alzheimer’s and Dementia and presented during this week’s Alzheimer’s Association International Conference in Boston, said the research confirms tests that had been done earlier on animals.
“In Alzheimer’s disease, the brain shows low levels of insulin, which is important for memory function,” she said. “One theory is that brain cells become insulin resistant, which is a feature of diabetes. The brain can’t take up the sugar it needs, because it is not responding to insulin, or insulin levels in the brain may be low.”
Bendlin said the WRAP participants, with an average age of 60, had no health or cognitive problems. They were given brain scans, and tests of their blood, fasting glucose and insulin levels, and cognitive abilities. The participants had a range of insulin resistance, which refers to the ability of the body’s cells to respond to insulin and is a feature of diabetes. In people with higher insulin resistance, the brain took up less sugar during the brain scan.
“We saw that they had lower intake of sugar in specific regions of the brain that are important for memory,” Bendlin said. “When we tested their cognition, we gave them words and asked them to repeat them. We could see in those people with higher levels of insulin resistance that they have lower glucose intake and poorer performance on their memory tests. Our study is unique because the participants are in midlife and they are mostly pre-diabetes. Also, this is definitely the largest study, involving 150 people.”
“The hypothesis is that diabetes is a risk factor for Alzheimer’s disease, but not everyone with diabetes is going to get Alzheimer’s,” she added. “We’re interested in how early interventions could protect people, and one of the things you could do to protect your brain is maintain proper blood sugar levels.”
According to the American Diabetes Association, 27 percent of people aged 65 and older in the U.S. have diabetes and about half have pre-diabetes. People with diabetes face double the risk of developing Alzheimer’s disease.
University of Wisconsin School of Medicine and Public Health