The Association of a Frailty Index and Incident Delirium in Older Hospitalized Patients: An Observational Cohort Study

Clin Interv Aging. 2020 Nov 2:15:2053-2061. doi: 10.2147/CIA.S249284. eCollection 2020.

Abstract

Introduction/background: Frailty identifies patients that have vulnerability to stress. Acute illness and hospitalization are stressors that may result in delirium and further accelerate the negative consequences of frailty.

Purpose: The purpose of this study was to determine whether frailty, identified at hospital admission and as measured by a frailty index, is associated with incident delirium.

Methods: A retrospective, observational, cohort study was done at a Veterans hospital between January 2013 and March 2014. English-speaking patients over 55 years were eligible. Exclusion criteria included inability to complete baseline assessments due to pre-existing cognitive impairment, emergent surgery; and/or admission from a nursing home, pre-existing delirium, and those with psychiatric disease or substance use disorder.

Main outcomes and measures: Frailty index (FI) variables included cognitive screening, physical function and comorbidities. The FI was calculated as a proportion of possible deficits (range 0 to 1; higher scores indicate increased frailty). Incident delirium was measured daily by an expert clinician interview.

Results: A total of 247 patients were admitted and 218 met inclusion/exclusion criteria, with a mean age of 71.54 years (SD = 9.53 years) and were predominantly white (92.7%) and male (91.7%). Participants were grouped using FI ranges as non-frail (FI <0.25, n=56 (26%)), pre-frail (FI =0.25-0.35, n=86 (39%)), and frail (FI >0.35, n=76 (35%)). Pre-frailty and frailty were associated with incident delirium (non-frail: 3.6% vs pre-frail: 20.9% vs frail: 29.3%, p=0.001) and total delirium days (mean day =non-frail 0.04 vs pre-frail 0.35 vs frail 0.57, p=0.003). After adjustment for sociodemographic factors, pre-frail (adjusted OR=5.64, 95% CI: 1.23, 25.99) and frail status (adjusted OR=6.80, 95% CI: 1.38, 33.45) were independently associated with delirium.

Conclusion: This study demonstrates that a frailty index is independently associated with incident delirium and suggests that admission assessments for frailty may identify patients at high risk of developing delirium.

Keywords: Veterans; delirium; frailty; frailty index; hospital.

Publication types

  • Observational Study

MeSH terms

  • Aged
  • Aged, 80 and over
  • Cohort Studies
  • Comorbidity
  • Delirium / diagnosis*
  • Delirium / epidemiology
  • Female
  • Frail Elderly / statistics & numerical data*
  • Frailty / epidemiology*
  • Geriatric Assessment / statistics & numerical data
  • Hospitalization / statistics & numerical data*
  • Humans
  • Male
  • Mental Health
  • Retrospective Studies
  • Risk Assessment
  • Risk Factors

Grants and funding

This work was funded by the VA Health Services Research and Development Center of Innovation in Long Term Services and Supports (CIN 13-419), VA Office of Academic Affiliation (Dr. Madrigal’s Advanced Fellowship in Health Services Research), and National Institutes of Health R56AG055833. Drs Sillner, Madrigal and Rudolph and Mr. McCongehy are employees of the United States Department of Veterans Affairs. The statements and opinions expressed are those of the authors and do not represent the official policy or procedures of the United States Government or the Department of Veterans Affairs.