The parts of the brain that young, healthy people use when daydreaming are the same areas that fail in people who have Alzheimer’s disease, researchers reported on Wednesday in a study that may someday help in preventing or diagnosing the disease.

The study, published in the Journal of Neuroscience, suggests that the way people use their brains could actually lead to Alzheimer’s disease.

“It may be the normal cognitive function of the brain that leads to Alzheimer’s later in life.

This was not a relationship we had even considered,” said Randy Buckner, a Howard Hughes Medical Institute investigator at Washington University in St. Louis who led the study.

The relationships are not clear and do not yet suggest that daydreaming is dangerous, but further study may shed light on the relationship, the study said.

The study found that Alzheimer’s mostly affects the brain’s “default state” regions - used when musing or daydreaming.

“We appear to use memory systems often in our default states,” Buckner said in a statement. “This may help us to plan and solve problems. Maybe it helps us be creative. But it may also have metabolic consequences.”

For their study, Buckner and colleagues used five different imaging techniques including positron emission tomography (PET) and magnetic resonance imaging (MRI) to study the brain activity of 764 volunteers, including those with Alzheimer’s, those close to developing dementia, and healthy people.

Such imaging scans have recently been found to indicate Alzheimer’s disease and may even be able to diagnose it - something that so far doctors can only do with 100 percent accuracy after death, although certain cognitive tests give a very good indication.

When people are concentrating on a task such as reading, talking or solving problems, the brain uses one set of regions, but during down time it switches to a default mode.

“The regions of the brain we tend to use in our default state when we are young are very similar to the regions where plaques form in older people with Alzheimer’s disease,” Buckner said.

Alzheimer’s has no cure and there are no long-lasting treatments for the brain-destroying illness, which affects an estimated 4.5 million Americans.

It is marked by a messy buildup in the brain of two proteins called beta-amyloid and tau, and the death of healthy brain cells, but the precise mechanisms are not understood.

Exercise, and mental and social activity appear to help protect some people against the disease.

The researchers said their imaging studies also helped show that people with pre-dementia had damage in areas known to be damaged in Alzheimer’s, which further confirms the potential use of brain imaging to diagnose and track the illness.