Researchers in the US believe they have found a link between structural changes in the brain and small declines in cognitive ability.
The scientists from the Mayo Clinic in Minnesota claim that mild cognitive impairment, which is thought to be a strong indication of an increased risk in developing Alzheimer's, shows itself in small tangles and plaques in small areas of the brain.
These plaques and tangles are far more widespread in fully developed Alzheimer's.
"I think our study provides an anatomical basis for the clinical condition of mild cognitive impairment. This shows that there are structural changes in the brains of people who may develop Alzheimer's disease," Dr Joseph Parisi, a neuropathologist at the Mayo Clinic, said in a statement.
The findings, published in the Archives of Neurology, were based upon autopsies of 15 people who had had mild cognitive impairment, 23 thought to have had Alzheimer's and 28 people without any cognitive problems.