WASHINGTON (AFP) – People with Alzheimer's disease may start experiencing shrinking of parts of the brain as many as 10 years before the degenerative condition is diagnosed, a US study suggested on Wednesday.

While the results are still preliminary, scientists said the findings could one day provide a way to identify by MRI scan which individuals are most likely to develop the disease, which can run in families and has no cure.

US researchers followed two separate groups of people who had no signs of Alzheimer's -- one group of 33 was tracked for 11 years and another group of 33 was followed for eight years.

Magnetic resonance imaging scans were performed regularly and focused on parts of the brain where Alzheimer's is typically found, such as the language and memory centers.

Over time, eight people in the first group and seven in the other developed the devastating condition.

When researchers looked back at their brain scans, they found early signs of shrinkage, or low MRI measurements, in the ones who would develop the disease.

"Of the 11 people who had the lowest MRI measurements, 55 percent developed Alzheimer's, while none of the nine people with the highest measurements developed dementia," said the study in Neurology, the medical journal of the American Academy of Neurology.

Twenty percent of those with average brain measurements developed the disease.

"This measure is potentially an important imaging marker of early changes in the brain associated with Alzheimer's disease that could help predict who might develop the dementia associated with this disease and possibly even how long it would be before dementia develops," said study author Bradford Dickerson of Harvard Medical School in Boston.

Alzheimer's is a progressive brain disease that causes memory loss and behavioral changes. It attacks the brain and gradually eats away at gray matter.

Alzheimer's is the most common form of dementia and is estimated to affect about five million Americans.