*3.1. Demographics*

In the full sample, 59.0% were male, 53.5% had premorbid ID in the mild range, and 46.5% in the moderate ID range. Most participants were white (86.1%), followed by Hispanic (6.9%), Asian (4.2%), Black (2.1%), and American Indian (0.7%). In terms of chromosomal diagnosis, 84.0% had full trisomy 21, 4.9% were mosaic, 3.5% had translocation DS, and 7.7% were unknown. Regarding AD status, 71.5% were CS and 28.5% were MCI-DS. The MCI-DS group was significantly older, z = −3.39, *p* = 0.0001, and were reported to have more co-occurring health problems than the CS group, but the rates of chronic medical conditions did not differ significantly (*p*s = 0.126 to 0.894, see Table 1).

**Table 1.** Demographic and health comorbidities by AD status.

