Neurocognitive disorder is a general term that describes decreased mental function due to a medical disease other than a psychiatric illness. It is often used synonymously (but incorrectly) with dementia. Alzheimer's disease is the most common cause of neurocognitive disorder. It affects between 60 and 80 percent of all people with dementia. Alzheimer's currently affects some 5.5 million people in the United States (U.S.) Cholinesterase inhibitors and memantine are primarily used in dementias to help slow cognitive decline. Cholinesterase inhibitors are recommended for neurocognitive disorders due to Parkinson disease, Lewy body disease, and Alzheimer disease, whereas memantine is indicated only for moderate to severe Alzheimer disease.