The LEADS study is exploring how early-onset Alzheimer's Disease (EOAD) progresses in people aged 40-64. This study is not a treatment but looks at how the disease develops naturally over time. Participants could have Alzheimer's, another cognitive condition, or no memory issues at all. Around 1350 people will join from the US and other countries. The study lasts 48+ months for those with memory issues and 24+ months for those without. Participants will have tests on their thinking skills, brain scans, and optional spinal fluid collection. They might also consider donating their brain for research after they pass away.

• Study Duration: 24-48+ months, depending on cognitive status.
• No treatments are involved; it's a natural progression study.
• Includes brain scans and optional spinal fluid tests.

Eligibility for the study includes having a study partner who knows you well, not being pregnant, and being able to speak English or Spanish. People who have certain medical conditions or histories may not be eligible to join. Participants will help scientists understand Alzheimer's better without receiving any medical treatment from the study.