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Development and Validation of a Predictive Model

Sharon K. Inouye, MD, MPH; Ying Zhang, MD, MPH; Richard N. Jones, ScD; Dan K. Kiely, MPH, MA; Frances Yang, PhD; Edward R. Marcantonio, MD, SM

Arch Intern Med. 2007;167(13):1406-1413.

Background  Persistent delirium at the time of hospital discharge is associated with poor outcomes. The objectives of this study were to develop and validate a predictive model for persistent delirium at hospital discharge.

Methods  This study followed a prospective validation design. For the development cohort, 491 consecutive patients 70 years or older admitted to the hospital without delirium and surviving to discharge were enrolled from the general medical units of an academic teaching hospital. For the validation cohort, 461 comparable subjects were enrolled. Twenty-two candidate risk factors were examined, including 12 baseline factors (present on admission) and 10 precipitating factors (hospital related). The primary outcome was delirium at hospital discharge, measured by the Confusion Assessment Method.

Results  Delirium at discharge was present in 58 patients (11.8%) in the development cohort. Five independent risk factors for delirium at discharge were identified: dementia (odds ratio [OR], 2.3; 95% confidence interval [CI], 1.4-3.7); vision impairment (OR, 2.1; 95% CI, 1.3-3.2); functional impairment (OR, 1.7; 95% CI, 1.2-3.0); high comorbidity (OR, 1.7; 95% CI, 1.1-2.6); and use of physical restraints during delirium (OR, 3.2; 95% CI, 1.9-5.2). A risk stratification system was created by adding 1 point for each factor present. Rates of delirium for the low-risk (0-1 factors), intermediate-risk (2-3 factors), and high-risk (4-5 factors) groups were 4%, 18%, and 63%, respectively (P < .001). The corresponding rates in the validation cohort, where 28 patients (6.1%) had delirium at discharge, were 3%, 14%, and 27% (P < .001).

Conclusions  A predictive model based on 5 risk factors has been successfully validated for prediction of delirium at discharge in hospitalized older patients. At least 4 of these risk factors are amenable to intervention strategies.

Author Affiliations: Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School (Drs Inouye, Jones, and Marcantonio), the Aging Brain Center, Institute for Aging Research, Hebrew SeniorLife (Drs Inouye, Zhang, Jones, Yang, and Marcantonio and Mr Kiely), and Department of Psychiatry, Brigham and Women's Hospital (Dr Yang), Boston, Massachusetts.

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