Brain structure changes years before dementia or Alzheimer's disease begins

People who develop dementia or Alzheimer's disease experience brain structure changes years before any signs of memory loss begin, according to a study published in the April 17, 2007, issue of Neurology, the scientific journal of the American Academy of Neurology.

Researchers say these findings may help identify people at risk of developing mild cognitive impairment (MCI), which leads to Alzheimer's disease.

Researchers performed brain scans and cognitive tests on 136 people over the age of 65 who were considered cognitively normal at the beginning of the five-year study. Participants were then followed annually with neurologic examination and extensive mental status testing. By the end of the study, 23 people had developed MCI, and nine of the 23 went on to be diagnosed with Alzheimer's disease. The brain scans of the 23 people with memory loss were then compared to the 113 people who remained cognitively normal.

Compared to the group that didn't develop memory problems, the 23 people who developed MCI or Alzheimer's disease had less gray matter in key memory processing areas of their brains even at the beginning of the study when they were cognitively normal.

"We found that changes in brain structure are present in clinically normal people an average of four years before MCI diagnosis," said study author Charles D. Smith, MD, with the University of Kentucky Medical Center in Lexington and member of the American Academy of Neurology. "We knew that people with MCI or Alzheimer's disease had less brain volume, but before now we didn't know if these brain structure changes existed, and to what degree, before memory loss begins."

In addition, the study found those people destined to develop MCI had lower cognitive test scores at the beginning of the study compared to the group that didn't develop memory problems, even though these scores were still within normal range.

"These findings of structural changes in cognitively normal people before memory loss begins aren't surprising given Alzheimer's disease may be present for many years before symptoms of the disease begin to appear," said Smith.