Goal Attainment Scaling (GAS) Sub-Study

People with Down syndrome are living longer. A longer life increases the chances of age-related risks of developing Alzheimer's disease and other forms of dementia. There is also growing evidence that people with Down syndrome respond differently to treatment than people without Down syndrome. This creates an important need to create a way to identify and follow changes in thinking and behavior as people with Down syndrome age and start to experience symptoms of dementia. Here, the investigators are testing a new method to monitor changes (in thinking and behavior) called goal attainment scaling. During this study, the participant will be asked to take part in a goal attainment scaling interview, which means working with a clinical rater (the participant's health care provider or other study team) to identify personally meaningful goals to follow for the study. "Goals" are based on symptoms or challenges experienced by the person for whom cares for the participant with Down Syndrome. The identified goals may be related to potential early signs and symptoms of Alzheimer's disease. These goals will then be reviewed at 2 time-points over the next 16 months. The investigators want to learn whether this type of interview can help the investigators understand what symptoms or challenges are important to the participant and whether this type of interview can help the investigators understand how these might change over time. The investigators also want to hear the participant's feedback about the participant's experience with goal attainment scaling at the end of the sub-study. The investigators will be asking about 45 participants to take part in this study. This study is observational and does not test a study drug.