Does Alzheimer's Disease and Related Dementias Modify Delirium Severity and Hospital Outcomes?

OBJECTIVES: We examined the association between delirium severity and outcomes of delirium among persons with and without Alzheimer's disease and related dementias (ADRD). DESIGN: Prospective cohort study. SETTING: Academic tertiary medical center. PARTICIPANTS: A total of 352 medical and surgical patients. MEASUREMENTS: Delirium incidence and severity were rated daily using the Confusion Assessment Method (CAM) and CAM-Severity (CAM-S) score during hospitalization. Severe delirium was defined as a CAM-S Short Form score in the highest tertile (3-7 points out of 7). ADRD status was determined by a clinical consensus process. Clinical outcomes included prolonged length of stay (>6 d), discharge to post-acute nursing facility, any decline in activities of daily living (ADLs) at 1 month from prehospital baseline, ongoing nursing facility stay, and mortality. RESULTS: Patients with ADRD (n = 85 [24%]) had a significantly higher relative risk (RR) for incident delirium (RR = 2.31; 95% confidence interval [CI] = 1.64-3.28) and higher peak CAM-S scores (mean difference = 1.24 points; CI = .83-1.65; P < .001). Among patients with ADRD, severe delirium significantly increased the RR for nursing facility stay (RR = 2.22; CI = 1.05-4.69; P = .04) and increased the RR for mortality (RR = 2.10; CI = .89-4.98; P = .09). Among patients without ADRD, severe delirium was associated with a significantly increased risk for all poor outcomes except mortality including prolonged length of stay in the hospital (RR = 1.47; CI = 1.18-1.82) and discharge to a post-acute nursing facility (RR = 2.17; CI = 1.58-2.98) plus decline in ADLs (RR = 1.30; CI = 1.05-1.60) and nursing facility stay at 1 month (RR = 1.93; CI = 1.31-2.83). CONCLUSION: Severe delirium is associated with increased risk for poor clinical outcomes in patients with and without ADRD. In both groups, severe delirium increased risk of nursing home placement. In patients with ADRD, delirium was more severe and associated with a trend toward increased mortality at 1 month. Although the increased risk remains substantial by RR, the study had limited power to examine the rarer outcome of death.