Alzheimers disease, dementia, poor memory , mci -- what causes do they have in common?

Memory deficits: There is a chemical in the brain called acetylcholine which is deficient with aging, and that causes deficits in cognitive functions.

Not known: Alzheimer's disease is only one cause of dementia and there are other causes of memory problem. Some are reversible (e.g., vitamin B12 deficiency) so it is important to exclude them by medical examination. Mci may be a mild form of alzheimer's disease.