Development of a Database to Investigate Digital and Blood-Based Biomarkers and Their Relationship to Tau and Amyloid PET Imaging in Older Participants Who Are Cognitively Normal (CN), Have Mild Cognitive Impairment (MCI), or Have Mild-to-Moderate AD Dementia

Inclusion Criteria: Pre-screening Inclusion Criteria Participants must meet ALL of the following criteria to progress to Visit 1 (Screening): 1. Participant is between 60 to 90 years of age (inclusive) at the time of consent; and 2. Participant has a study partner who has sufficient and frequent contact with the participant (defined as at least 8 hours of contact a week) and is able to provide accurate information regarding the participant's cognitive and functional abilities. Core Study Inclusion Criteria Participants must meet ALL of the following criteria, in addition to the Pre-screening Inclusion Criteria, for entry into the study: 1. Participants must provide written consent in the IRB-approved or Ethics Committee (EC) approved informed consent form or have a legally authorized representative (LAR) provide written consent on the participant's behalf in accordance with local and national guidance and regulation; 2. Participants must be willing to undergo an MRI brain scan within 90 days and an amyloid and tau PET scan within 120 days of signing informed consent; 3. Participants must be willing to comply with all study procedures as outlined in the informed consent, including blood sampling, genetic testing, and storage of biospecimens for future research; 4. Fluency in the language of the tests used at the study site; 5. Participants must be willing to be contacted for possible participation in clinical research trials once their participation in this study ends; and 6. Participants must have a Mini-Mental State Exam (MMSE) score of 16 to 30 inclusive at screening. Exclusion Criteria: Pre-screening Exclusion Criteria Participants who meet ANY of the following criteria will not be eligible to progress to Visit 1 (Screening): 1. Participant is unable to undergo amyloid and tau PET scans due to self-reported pregnancy, sensitivity to ligands being used, poor venous access, contraindication to PET, or planned or recent exposure to ionizing radiation that in combination with the planned administration of amyloid radioligand would result in a cumulative exposure that exceeds recommended local guidelines; 2. Participants who have reported or have a known negative amyloid PET scan in the past 6 months; 3. Participants with any known contraindication to brain MRI scan; 4. Participants with history of stroke or seizures within 1 year of the Pre-Screening Visit; 5. Participants with history of cancer within the past 5 years with the exception of non-melanoma skin cancer or prostate cancer in situ; 6. Participants with known or suspected alcohol or drug abuse or dependence within 1 year of the Pre- Screening Visit; 7. Participants who report any current unstable psychiatric symptoms that could interfere with study procedures or impact study data (e.g., uncontrolled depression); 8. Participants who have received any potential disease modifying AD treatment within 6 months prior to the Pre-screening Visit; and 9. Participants with known history or self-report to be Human Immunodeficiency Virus (HIV) Positive unless controlled by antiviral medication. Core Study Exclusion Criteria Participants who meet ANY of the following criteria, in addition to the Pre-screening Exclusion Criteria, will not be eligible to enroll into the study: 1. Participants who, in the opinion of the Site Principal Investigator, have serious or unstable medical conditions that would prohibit their completion of all study procedures and data collection; 2. Participants who have serious or unstable medical conditions that would likely preclude their participation in an interventional research trial; 3. Participants with self-reported, untreated conditions such as vitamin B12 or folate deficiency or bladder infections that in the opinion of the Site Principal Investigator could contribute to cognitive impairment; 4. Participants who have completed cognitive testing within 1 month of Visit 1 (Screening) where the Site Principal Investigator believes the participant's exposure may cause practice effect; 5. Participants who have any neurological disorder affecting the central nervous system, other than AD, that may be contributing to cognitive impairment (e.g., Parkinson's disease, other dementias, multiple concussions or seizures) as deemed significant by the Site Principal Investigator; 6. Participants with a Geriatric Depression Scale (GDS) score greater than or equal to 8 at Visit 1 (Screening) and is deemed to be clinically significantly depressed by the Site Principal Investigator; 7. Participants with a Rey Auditory Verbal Learning Test (RAVLT) t-score of ≥ 1.2 standard deviation above the mean. For non-African Americans, calculate age-sex-education adjusted t-scores. For African American participants, use the MOANS to calculate the age-education adjusted t-scores; 8. Participants weighing less than 110 pounds; 9. Participants who are direct employees or family members of direct employees of the participating investigators' sites; 10. Participants who are direct employees of the Sponsor; 11. Participants who, in the opinion of the investigator, are unable to complete cognitive testing due to inadequate visual or auditory acuity; and 12. For participants completing the RetiSpec retinal scan: Those with a known history of contraindication or allergy to Tropicamide 1% (pupil dilation drop). Longitudinal Sub-Study Eligibility Inclusion Criteria: Participants must meet ALL of the following criteria for entry into the sub-study: 1. Participants who completed the Bio-Hermes-002 Core Study; 2. Are willing to complete phone call visits with site staff every three months and return to the clinic for an annual evaluation; and 3. Are willing to complete annual PET scans for both amyloid and tau scans. Exclusion Criteria: Participants who meet ANY of the following criteria will not be eligible for entry into the sub-study: 1. Those who are enrolled or intend to enroll into a clinical trial for Alzheimer's disease wit