A five-year study of the brains of 136 subjects showed that changes in the brain precede symptoms and diagnosis of cognitive impairment and Alzheimers.

The participants, all over the age of 65, ranked as cognitively normal on tests given at the start of the study. Brain scans of the participants were also taken at the start of the study. The participants were followed with neurological and cognitive testing over the study period.

At the end of the study, 23 participants had developed MCI (mild cognitive impairment) and, of those, 9 went on to be diagnosed with Alzheimers.

Researchers discovered that changes in the brain had taken place as much as four years before the subjects had started to show cognitive impairment. The brain scans showed a decrease in grey matter in those participants who went on to develop memory problems while they still tested normal for cognitive function.

Researchers hope that the results of the study will help in identifying people at risk of developing MCI which leads to Alzheimers.

The study is published in the April 17, 2007, issue of Neurology®, the scientific journal of the American Academy of Neurology.