δ scores predict multiple neuropsychiatric symptoms

Dementia severity is strongly related to Spearman's general intelligence factor "g", via the latent dementia phenotype "δ" and is distinct from domain-specific cognitive impairments arising from disease-specific regional pathologies. It is an empiric question whether behavioral and psychological symptoms of dementia (BPSD) are associated with δ or with domain-specific constructs.

A recently developed δ homolog ("dDx") was tested as a predictor of 1 year prospective BPSD in n = 723 Mexican-American and non-Hispanic White participants in the Texas Alzheimer's Research and Care Consortium (TARCC). The informant-rated frequencies of 12 BPSD were rated by the neuropsychiatric inventory (NPI-Q). Baseline BPSD, demographic features, selected biomarkers, and treatment exposure to acetylcholinesterase inhibitors were used as covariates. Composite scores derived from orthogonal latent measures of domain-specific memory (MEM) and executive function (EF) were also tested as predictors.

"Functionally salient cognitive impairment (FSCI)" that is, categorical "dementia" as diagnosed by dDx was associated with increased prospective frequency of 11/12 BPSD, independently of baseline behavior and covariates. Age, depressive symptoms, and EF were associated with individual BPSD. MEM was not associated with any. Dementia severity, as measured by dDx, was also associated with a prospective increase in total NPI-Q scores.

δ is associated non-specifically with multiple BPSD. This suggests the existence of a dementia-specific behavioral profile, arising from insults to general intelligence, and unrelated to disease-specific regional pathology(ies).