What causes cognitive impairment?

There is no single cause of mild cognitive impairment though researchers believe it often comes from changes in the brain similar to those seen in Alzheimer's disease, according to Mayo Clinic. The changes seen with mild cognitive impairment are less severe than those found in Alzheimer's.

Some of the changes that are often seen as the possible cause of mild cognitive impairment are not always evident until autopsy, explains Mayo Clinic. One such change is the formation of plaque clumps in the brain, a sign of Alzheimer's disease. Another change is the development of Lewy bodies, microscopic clumps of protein that are also associated with Parkinson's disease, in some cases of Alzheimer's and in other types of dementia.

Another change that may be associated with mild cognitive impairment includes the shrinking of the hippocampus, a part of the brain associated with memory, which may cause mild cognitive impairment, states Mayo Clinic. The enlargement of ventricles, fluid-filled spaces, in the brain may also be associated with this condition. It is also possible that the brain has reduced its need for glucose, an important energy source for cells, in some of the key areas of the brain. There also may be a buildup of plaque in the brain.