NEW YORK (Reuters Health) — In normal older individuals, MRI of the brain reveals loss of grey matter about four years before symptoms of mild cognitive impairment set in, according to results of a study reported in the medical journal Neurology.

The study subjects included 136 volunteers who were at least 65 years old and were considered to have normal neurological function when the study began, according to the researchers at the University of Kentucky Medical Center in Lexington.

The subjects underwent a battery of tests each year, and a complete physical and neurological examination was conducted semi-annually, along with functional assessments. In 1999, MRI scans of the brain were performed.

During an average follow-up of 5.4 years, 23 subjects were diagnosed with cognitive impairment, and nine of these subjects had developed Alzheimer’s disease. Those who became impaired had lower scores on several of the cognitive tests compared with subjects who remained normal.

The MRIs of subjects destined to be diagnosed with mild cognitive impairment also had significant volume reductions in areas of the brain associated with memory processing, the authors report.

Brain structure changes can be seen in clinically normal people an average of 4 years before they are diagnosed with mild cognitive impairment, lead author Dr. Charles D. Smith concluded.