Background: Overlap between neuropsychiatric symptoms of dementia and delirium complicates diagnosis of delirium superimposed on dementia (DSD). This study sought to examine differences in delirium presentation and outcomes between DSD patients with and without pre-existing behavioral and psychological symptoms of dementia (BPSD).
Methods: This was a prospective cohort study of older adults with DSD admitted to a specialized delirium unit (December 2010–August 2012). We collected data on demographics, comorbidities, illness severity, delirium precipitants, and cognitive and functional scores. Delirium severity was assessed using Delirium Rating Scale Revised-98 (DRS-R-98) and Cognitive Assessment Method severity score (CAM-sev). Patients were categorized as DSD–BPSD+ and DSD–BPSD− based on elicited behavioral and psychological disturbances.
Results: We recruited 174 patients with DSD (84.4 +/−7.4 years) with 37 (21.3%) having BPSD. At presentation, delirium severity and symptom frequency on DRS-R98 were similar, but DSD–BPSD+ more often required only a single precipitant (40.5% vs. 21.9%, p = 0.07), and had significantly longer delirium duration (median days: 7 vs. 5, p < 0.01). At delirium resolution, DSD–BPSD+ exhibited significant improvement in sleep–wake disturbances (89.2% vs. 54.1%, p < 0.01), affect lability (81.1% vs. 56.8%, p = 0.05), and motor agitation (73% vs. 40.5%, p < 0.01), while all non-cognitive symptoms except motor retardation were improved in DSD–BPSD−. Pharmacological restraint was more prevalent (62.2% vs. 40.1%, p = 0.03), and at higher doses (chlorpromazine equivalents 0.95 +/−1.8 vs. 0.40 +/−1.2, p < 0.01) in DSD–BPSD+.
Conclusions: BPSD may increase vulnerability of dementia patients to delirium, with subsequent slower delirium recovery. Aggravation of sleep disturbance, labile affect, and motor agitation should raise suspicion for delirium among these patients.