Dementia occurs for different reasons in diabetics and non-diabetics, state researchers.
Dementia in some diabetics appears to be caused often by vascular disease in the brain, while in people without diabetes it is more likely associated with deposition of the plaque seen in people with Alzheimer's disease.
"It suggests that the vascular dementia seen in diabetics, which appears to be related to small blood vessel disease and strokes, can potentially be averted if development of diabetes is prevented," says Mayo neurologist Neill Graff-Radford.
The scientists measured the ratio of two different kinds of amyloid beta proteins in blood.
Plaque found in the brains of Alzheimer's disease patients at autopsy started when the toxic form of amyloid beta, known as AB42, began to be deposited.
Researchers found that among non-diabetics, only the AB42/AB40 low ratio was associated with dementia.
In diabetics, the ratio of AB42 to AB40 was not decreased.
"We now propose that future studies of this test should take into account diabetic status," Radford says.