Pathway from Delirium to Death: Potential In-Hospital Mediators of Excess Mortality

Abstract

Objectives: (1) To determine the relationship of incident delirium during hospitalization with 90-day mortality; (2) to identify potential in-hospital mediators through which delirium increases 90-day mortality.

Design: Analysis of data from Project Recovery, a controlled clinical trial of a delirium prevention intervention from 1995 to 1998 with follow-up through 2000.

Setting: Large academic hospital.

Participants: Patients ≥70 years old without delirium at hospital admission who were at intermediate-to-high risk of developing delirium and received usual care only.

Measurements: (1) Incident delirium; (2) potential mediators of delirium on death including use of restraining devices (physical restraints, urinary catheters), development of hospital acquired conditions (HACs) (falls, pressure ulcers), and exposure to other noxious insults (sleep deprivation, acute malnutrition, dehydration, aspiration pneumonia); (3) death within 90 days of admission.

Results: Among 469 patients, 70 (15%) developed incident delirium. These patients were more likely to experience restraining devices (37% vs 16%, P < .001), HACs (37% vs 12%, P < .001), other noxious insults (63% vs 49%, P = .03), and 90-day mortality (24% vs 6%, P < .001). The inverse probability weighted hazard of death due to delirium was 4.2 (95% CI = 2.8-6.3) in bivariable analyses, increased in a graded manner with additional exposures to restraining devices, HACs, and other noxious insults, and declined by 10.9% after addition of these potential mediator categories, providing evidence of mediation.

Conclusion: Restraining devices, HACs, and additional noxious insults were more frequent among patients with delirium, increased mortality in a graded manner, and were responsible for a significant percentage of the association of delirium with death. Additional efforts to prevent potential downstream mediators through which delirium increases mortality may help to improve outcomes among hospitalized older adults.

Keywords: delirium; geriatrics; hospital care; hospital-acquired conditions; quality of care.

Figure 1. Cumulative Hazard of Death Associated with Delirium and the Number of Adverse Hospital Exposures

The left panel shows data for the cumulative hazard of death associated with incident delirium in the 90 days after hospital admission. Results are adjusted for the presence of adverse hospital exposures, which include the use of physical restraints, use of a urinary catheter, occurrence of a fall, occurrence of a pressure ulcer, occurrence of sleep deprivation, occurrence of acute malnutrition, occurrence of dehydration, and occurrence of aspiration pneumonia. The right panel shows data for the cumulative hazard of death associated with the number of adverse hospital exposures, which include the use of physical restraints, use of a urinary catheter, occurrence of a fall, occurrence of a pressure ulcer, occurrence of sleep deprivation, occurrence of acute malnutrition, occurrence of dehydration, and occurrence of aspiration pneumonia. Results are adjusted for the presence of incident delirium. AHE=Adverse Hospital Exposure.