Delirium: Prevalence and outcome in the very old in 27 medical departments during a one-year prospective study.

Objective: The prevalence and effects of delirium in very old individuals aged ≥80 years have not yet been systematically evaluated. Therefore, this large single-center study of the one-year prevalence of delirium in 3,076 patients in 27 medical departments of the University Hospital of Zurich was conducted.

Methods: Patient scores on the Delirium Observation Screening scale, Intensive Care Delirium Screening Checklist, , and electronic Patient Assessment-Acute Care (nursing tool) resulted in the inclusion of 3,076 individuals in 27 departments. The prevalence rates were determined by simple logistic regressions, odds ratios (ORs), and confidence intervals.

Results: Of the 3,076 patients, 1,285 (41.8%) developed delirium. The prevalence rates in the 27 departments ranged from 15% in rheumatology (OR = 0.30) to 73% in intensive care (OR = 5.25). Delirious patients were more likely to have been admitted from long-term care facilities (OR = 2.26) or because of emergencies (OR = 2.24). The length of their hospital stay was twice as long as that for other patients. Some died before discharge (OR = 24.88), and others were discharged to nursing homes (OR = 2.96) or assisted living facilities (OR = 2.2).

Conclusion: This is the largest study to date regarding the prevalence of delirium in patients aged ≥80 years and the medical characteristics of these patients. Almost two out of five patients developed delirium, with a high risk of loss of independence and mortality.