(CBS) Add Alzheimer's to the list of diseases linked to unhealthy eating. A new study links high cholesterol to the degenerative neurological disorder, which affects 5.4 million Americans.
"We found that high cholesterol levels were significantly related to brain plaques associated with Alzheimer's disease," study author Dr. Kensuke Sasaki, researcher at Kyushu University in Fukuoka, Japan, said in a written statement.
For the study - published in the September 12 issue of Neurology - researchers tested cholesterol levels for nearly 2,600 people between the ages of 40 and 79 who had no signs of Alzheimer's. The researchers checked in on participants 10 to 15 years later and performed autopsies on 147 people who died, and found 34 percent of those people had been diagnosed with dementia. The autopsies also showed the hallmark plaques and tangles, representative of protein buildup in the brain.
The key finding? Eighty-six percent of people with high cholesterol had these brain plaques. Only 62 percent of people with low cholesterol had them.
The finding raises an interesting question: Can Alzheimer's be treated with cholesterol-lowering drugs?
Alas, probably not.
"Our study clearly makes the point that high cholesterol may contribute directly or indirectly to plaques in the brain," Sasaki said, "but failed treatment trials of cholesterol-lowering drugs in Alzheimer's disease means there is no simple link between lowering cholesterol and preventing Alzheimer's."
What might work? Insulin, according to another study, published September 12 issue of Archives of Neurology.
Researchers at the University of Washington tested a nasal insulin spray on patients with either Alzheimer's, or a milder form of dementia known as mild cognitive impairment, giving them a nasal spray containing either insulin or placebo. Previous research has shown insulin activity is reduced in patients with Alzheimer's, so the researchers wanted to see if the spray would improve cognition.
Patients given a smaller dose of daily insulin were better able to recount details of a story in a memory test, and patients on small and large doses improved slightly or remained the same in terms of cognitive function. Placebo-takers got much worse. The insulin also appeared to prevent protein buildup when researchers tested patients' spinal fluids.
Though the findings are provocative, some experts caution that an insulin treatment for Alzheimer's is unlikely to be available anytime soon
"It's important readers realize this is a pilot trial," said Dr. P. Murali Doraiswamy, a professor of neurology at Duke University, who was not part of the study, told the New York Times. "It's not ready for prime time."
Alzheimer's is the sixth-leading cause of death in the U.S. By 2050, as many as 16 million Americans will have the disease, according to the Alzheimer's Association. Alzheimer's risk is increased with diabetes, low education, obesity, depression, and smoking.