heimer’s disease are between ages 65 and 74 years, 53% are between ages 75 and 84 years,
and 40% are 85 years and older. The percentage  of dementias attributable to Alzheimer’s
disease ranges from about 60% to over 90%, depending on the setting and diagnostic cri-
teria. Mild NCD due to Alzheimer’s disease is likely to represent a substantial fraction of
mild cognitive impairment (MCI) as well.
Development and Course
Major or mild NCD due to Alzheimer’s disease progresses gradually, sometimes with
brief plateaus, through severe dementia to death. The mean duration of survival after di-