Table 4.

General linear mixed models of premorbid intellectual disability (ID) level and clinical Alzheimer’s disease Status and their interaction on age

	Estimate (Standard Error) or F value
Site (random effect)	21.909 (<0.001)**
Trisomy type (versus full)	3.928 (0.021)
Mosaicism	3.079 (1.970)
Translocation	–3.891 (1.726)*
APOE ɛ4	–2.596 (0.947)*
Biological Sex	–1.234 (0.841)*
Clinical Status (versus CS)	13.901 (<0.001)**
MCI-DS	6.602 (1.804)**
Dementia	8.446 (1.771)**
Premorbid ID (versus mild)	0.999 (0.369)
Moderate	–0.670 (1.018)
Severe/Profound	1.508 (1.585)
Premorbid ID×Clinical Status (versus CS)	1.531 (0.193)
Moderate×MCI-DS	–2.626 (2.504)
Moderate×Dementia	0.389 (2.757)
Severe/Profound×MCI-DS	4.548 (4.703)
Severe/Profound×Dementia	–6.321 (4.227)

ID, intellectual disability; CS, cognitively stable; MCI-DS, mild cognitive impairment-Down syndrome; Aβ, amyloid-beta assessed in centiloids. ^*p < 0.05; ^**p < 0.01.