RecruitingAmyloid PET Imaging in the Baltimore Longitudinal Study of AgingBackground: Some people experience cognitive decline as they age. That is, they lose memory, problem-solving, and other mental abilities. Amyloids are groups of proteins that develop in the brain and increase in number as people age. Researchers want to use imaging scans to track amyloids in people s brains over time. Their goal is to find out if any changes are related to cognitive decline or other medical issues. Objective: To learn how amyloids may affect brain structure and function as people age. Eligibility: People aged 55 years and older who are enrolled in the Baltimore Longitudinal Study of Aging. Design: Participants will have imaging scans and other tests every 1 to 4 years, depending on their age. Those 80 and older will be scanned yearly. These scans will be done during regular BLSA visits. The scans will be positron emission tomography and computed tomography (PET CT). Participants will be given fluid through a tube inserted into a vein in their arm. The fluid is a tracer that will cause the amyloids to light up in the images. Then they will lie on a bed with their head inside a PET CT scanner. They will lie still for about 30 minutes. Participants will have tests to assess their memory and other mental skills. They will answer questions about their mood and daily life. These tests will take about 40 minutes to complete; they may be done in person or by phone. Participants will give a contact number for someone who can answer questions about the participant s daily routine. These questions may be answered in person or by phone. Participants will be in this study for 5 years.