Impact of behavioral subsyndromes on cognitive decline in Alzheimer's disease: data from the ICTUS study

Behavioral and psychological symptoms of dementia (BPSD) represent common manifestations among patients affected by Alzheimer's disease (AD). Some reports have recently classified BPSD into specific clusters/subsyndromes exploring the internal structure of the Neuropsychiatric Inventory (NPI). We evaluated whether specific behavioral subsyndromes are associated with worsening cognitive function. Mild to moderate AD patients were recruited from the cohort of the Impact of Cholinergic Treatment USe (ICTUS) study. Neuropsychiatric symptoms were classified in three subsyndromes, identified at baseline, grouping different combinations of NPI items: (1) "psychotic" ("delusions" and/or "hallucinations"); (2) "affective" ("agitation" and/or "depression" and/or "anxiety" and/or "irritability"); and (3) "behavioral" ("euphoria" and/or "apathy" and/or "disinhibition" and/or "aberrant motor behavior"). Mixed model analyses were performed to measure six-monthly changes in the ADAS-Cog score over a follow-up of 2 years, according to these subsyndromes. All analyses were stratified according to AD severity as defined by the Clinical Dementia Rating (CDR). A total of 1,375 AD subjects were recruited. No NPI cluster was found to significantly (p < 0.05) affect the rate of cognitive decline across the 3 CDR classes. Our results suggest that the cognitive course of AD is not substantially influenced by the presence of specific neuropsychiatric phenotypes. Further studies are needed to extend the present findings and identify possible biological and clinical bases for behavioral subsyndromes.