RecruitingADRC Clinical Cohort (Alzheimer's Disease)The purpose of the study is to establish a clinical cohort for the Duke/UNC Alzheimer's Disease Research Center (ADRC). The cohort will be composed of subjects ages 25 to 44 at enrollment with normal cognition and subjects ages 45 to 80 at enrollment with normal cognition, mild cognitive impairment, or a dementia diagnosis. Initial data including demographics, medical and family history, physical exam, and neuropsychological testing will be obtained. Participants will be asked to contribute a blood sample, a urine sample, a cerebrospinal fluid sample, and undergo a MRI scan. The cohort ages 45 to 80 will be seen yearly until death to evaluate medical status, undergo neuropsychological testing and possibly collect additional samples or undergo additional imaging. All data will be de-identified and stored by the ADRC. The purpose of this study is to examine normal cognition, mild cognitive impairment and Alzheimer's disease and related dementias (ADRD) as people get older. The investigators also hope to be able to assess risk factor information of the role of genes and environmental exposures (for example health conditions, diet, and medications) in Alzheimer's disease and related disorders (ADRD) and other conditions of aging. The biological samples collected in the study will create a repository. A repository is a collection of blood and tissue samples from people with certain diseases and conditions. For the purpose of this research, the investigators hope to help researchers learn more about Alzheimer's disease and related disorders and other conditions of aging.