Den gennemsnitlige levealder efter diagnosen stilles er omkring seks år.<ref name="pmid3776457">{{vcite journal | vauthors = Mölsä PK, Marttila RJ, Rinne UK | title = Survival and Cause of Death in Alzheimer's Disease and Multi-Infarct Dementia | journal = Acta Neurologica Scandinavica | volume = 74 | issue = 2 | pages = 103–07 | year = 1986 | pmid = 3776457 | doi = 10.1111/j.1600-0404.1986.tb04634.x | month = August }}</ref> Mindre end 3% af ramte personer lever længere end 14 år efter diagnosen.<ref name="pmid7793228">{{vcite journal | vauthors = Mölsä PK, Marttila RJ, Rinne UK | title = Long-Term Survival and Predictors of Mortality in Alzheimer's Disease and Multi-Infarct Dementia | journal = Acta Neurologica Scandinavica | volume = 91 | issue = 3 | pages = 159–64 | year = 1995 | pmid = 7793228 | month = March | doi=10.1111/j.1600-0404.1995.tb00426.x}}</ref> Blandt de sygdomsegenskaber, der især associeres med den større [[mortalitet]] er den alvorlige kognitive forringelse, sænket funktionelle niveau, mange problemer med at falde, samt forstyrrelser i den neurologiske undersøgelse <!-- "disturbances in the neurological examination" -->. Andre sammenfaldende sygdomme, såsom [[hjerte-kar-sygdomme|hjerteproblemer]], [[Diabetes mellitus|diabetes]] eller en fortid med [[alkoholmisbrug]] forbindes også med den forringede chance for at overleve.<ref name="pmid8757016">{{vcite journal | vauthors = Bowen JD, Malter AD, Sheppard L |display-authors=etal | title = Predictors of Mortality in Patients Diagnosed with Probable Alzheimer's Disease | journal = Neurology | volume = 47 | issue = 2 | pages = 433–39 | year = 1996 | pmid = 8757016 | doi = 10.1212/wnl.47.2.433 }}</ref><ref name="pmid15068977">{{vcite journal | vauthors = Larson EB, Shadlen MF, Wang L |display-authors=etal | title = Survival after Initial Diagnosis of Alzheimer Disease | journal = Annals of Internal Medicine | volume = 140 | issue = 7 | pages = 501–9 | year = 2004 | pmid = 15068977 | doi=10.7326/0003-4819-140-7-200404060-00008}}</ref><ref name="pmid7792352">{{vcite journal | vauthors = Jagger C, Clarke M, Stone A | title = Predictors of Survival with Alzheimer's Disease: A Community-based Study | journal = Psychological Medicine | volume = 25 | issue = 1 | pages = 171–7 | year = 1995 | pmid = 7792352 | doi = 10.1017/S0033291700028191 | month = January }}</ref> Selv om man får flere samlede antal års overlevelse hvis sygdommen rammer i en ung alder, er [[forventet levetid]] især reduceret når den sammenlignes med den tilsvarende sunde befolkning blandt yngre mennesker.<ref name="pmid12580712">{{vcite journal | vauthors = Dodge HH, Shen C, Pandav R, DeKosky ST, Ganguli M | title = Functional Transitions and Active Life Expectancy Associated with Alzheimer Disease | journal = Archives of Neurology | volume = 60 | issue = 2 | pages = 253–59 | year = 2003 | pmid = 12580712 | doi = 10.1001/archneur.60.2.253 | month = February }}</ref> Mænd har generelt en sværere prognose for overlevelse end kvinder.<ref name="pmid7793228"/><ref name="pmid15883266">{{vcite journal | vauthors = Ganguli M, Dodge HH, Shen C, Pandav RS, DeKosky ST | title = Alzheimer Disease and Mortality: A 15-year Epidemiological Study | journal = Archives of Neurology | volume = 62 | issue = 5 | pages = 779–84 | year = 2005 | pmid = 15883266 | doi = 10.1001/archneur.62.5.779 | month = May }}</ref>
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