Late Onset Alzheimer's Disease

Inclusion Criteria:

• Established diagnosis of definite or probable AD or have a diagnosis of a relatedneurodegenerative disorder such as Frontotemporal Dementia (FTD) or Lewy BodyDementia (LBD) (will also recruit sporadic FTD and LBD) cases.

• a living sibling with probable or possible AD;

• a third living relative affected with AD (onset age 50 or older) or unaffected (60or older);

• participants in the proband's generation with an identified companion serving as aninformant;

• participants who have capacity to consent or participants lacking capacity toconsent with a surrogate/proxy in place to provide consent.

Exclusion Criteria:

• failure to identify an appropriate informant;

• uncertainty of the clinical diagnosis of Alzheimer's disease or other relateddisorder;

• discovery of additional diagnosis that could account for the clinicalmanifestations;

• unwillingness to participate;

• failure to identify a living sibling with AD or other related disorder (except inthe cases of sporadic FTD and sporadic LBD);

• participants lacking the capacity to consent who do not have a surrogate or proxy ornext of kin to provide consent.