*Article* **Cognitive and Behavioral Domains That Reliably Differentiate Normal Aging and Dementia in Down Syndrome**

**Jordan P. Harp 1,\* , Lisa M. Koehl <sup>1</sup> , Kathryn L. Van Pelt <sup>2</sup> , Christy L. Hom <sup>3</sup> , Eric Doran <sup>4</sup> , Elizabeth Head <sup>5</sup> , Ira T. Lott <sup>6</sup> and Frederick A. Schmitt <sup>7</sup>**


**Abstract:** Primary care integration of Down syndrome (DS)-specific dementia screening is strongly advised. The current study employed principal components analysis (PCA) and classification and regression tree (CART) analyses to identify an abbreviated battery for dementia classification. Scale- and subscale-level scores from 141 participants (no dementia *n* = 68; probable Alzheimer's disease *n* = 73), for the Severe Impairment Battery (SIB), Dementia Scale for People with Learning Disabilities (DLD), and Vineland Adaptive Behavior Scales—Second Edition (Vineland-II) were analyzed. Two principle components (PC1, PC2) were identified with the odds of a probable dementia diagnosis increasing 2.54 times per PC1 unit increase and by 3.73 times per PC2 unit increase. CART analysis identified that the DLD sum of cognitive scores (SCS < 35 raw) and Vineland-II community subdomain (<36 raw) scores best classified dementia. No significant difference in the PCA versus CART area under the curve (AUC) was noted (D(65.196) = −0.57683; *p* = 0.57; PCA AUC = 0.87; CART AUC = 0.91). The PCA sensitivity was 80% and specificity was 70%; CART was 100% and specificity was 81%. These results support an abbreviated dementia screening battery to identify at-risk individuals with DS in primary care settings to guide specialized diagnostic referral.

**Keywords:** Down syndrome; dementia; cognition; functional independence; neuropsychological assessment; primary care; screening
