The purpose of this study is to determine if insulin-like growth factors (IGF) play a role in the development of dementia, specifically Alzheimer's disease (AD). The study will compare results from genetic testing between patients with AD and two other groups: younger biological family members of the AD patients and individuals without AD matched by age to the AD patients.

Inclusion Criteria:

• Men and women between the ages of 50 and 81 years old who have a diagnosis of dementia
• Men and women who are at least 18 years old and are biologically related to the study subject with dementia
• Control subjects must not have a diagnosis of dementia and must be matched in age to the study subjects with dementia

Exclusion Criteria:

• Biological family members of the dementia patient who are either younger than 17 years of age or older than the patient with dementia
• Biological family members with a diagnosis of dementia
• Age-matched control subjects with a diagnosis of dementia

There are three groups of participants for this research study: one group will consist of individuals diagnosed with dementia; another group will consist of younger biological family members of the patients with dementia; and the third group will consist of individuals without dementia who are matched in age to the patients with dementia.