typical clinical picture, without extended plat eaus or evidence of mixed etiology, can also
be diagnosed as due to probab le Alzheimer’s disease. For mild NCD, given the lesser de-
gree of certainty that the deficits will prog ress, these features are only sufficient for a
possible  Alzheimer’s etiology. If the etiology appe ars mixed, mild NCD due to multiple eti-
ologies should be diagnosed. In any case, for both mild and major NCD due to Alzhei-
mer’s disease, the clinical features must no t suggest another primary etiology for the NCD
(Criterion D). 
Associated Features Supporting Diagnosis
In specialty clinical settings, approximately 80% of individuals with major NCD due to
Alzheimer’s disease have behavioral and psyc hological manifestations; these features are
also frequent at the mild NCD stage of impa irment. These symptoms are as or more dis-
tressing than cognitive manifestations and ar e frequently the reason that health care is
sought. At the mild NCD stage or the mildest level of majo r NCD, depression and/or ap-
athy are often seen. With moderately severe major NCD, psychotic fe atures, irritability,
agitation, combativeness, and wandering are common. Late in the illness, gait distur-
bance, dysphagia, incontinence, myoc lonus, and seizures are observed.
Prevalence
The prevalence of overall deme ntia (major NCD) rises steeply with age. In high-income
countries, it ranges from 5% to 10% in the seventh decade to  at least 25% thereafter. U.S.
census data estimates suggest that approxim ately 7% of individuals diagnosed with Alz-