Delirium superimposed on dementia strongly predicts worse outcomes in older rehabilitation inpatients

Abstract

Objective: Delirium superimposed on dementia (DSD) is common in many settings. Nonetheless, little is known about the association between DSD and clinical outcomes. The study aim was to evaluate the association between DSD and related adverse outcomes at discharge from rehabilitation and at 1-year follow-up in older inpatients undergoing rehabilitation.

Design: Prospective cohort study.

Setting: Hospital rehabilitation unit.

Participants: A total of 2642 patients aged 65 years or older admitted between January 2002 and December 2006.

Measurements: Dementia predating rehabilitation admission was detected by DSM-III-R criteria. Delirium was diagnosed with the DSM-IV-TR. The primary outcome was that of walking dependence (Barthel Index mobility subitem score of <15) captured as a trajectory from discharge to 1-year follow-up. A mixed-effects multivariate logistic regression model was used to analyze the association between DSD and outcome, after adjusting for relevant covariates. Secondary outcomes were institutionalization and mortality at 1-year follow-up, and logistic regression models were used to analyze these associations.

Results: The median age was 77 years (interquartile range: 71-83). The prevalence of DSD was 8%, and the prevalence of delirium and dementia alone were 4% and 22%, respectively. DSD at admission was found to be significantly associated with almost a 15-fold increase in the odds of walking dependence (odds ratio [OR] 15.5; 95% Confidence Interval [CI] 5.6-42.7; P < .01). DSD was also significantly associated with a fivefold increase in the risk of institutionalization (OR 5.0; 95% CI 2.8-8.9; P < .01) and an almost twofold increase in the risk of mortality (OR 1.8; 95% CI 1.1-2.8; P = .01).

Conclusions: DSD is a strong predictor of functional dependence, institutionalization, and mortality in older patients admitted to a rehabilitation setting, suggesting that strategies to detect DSD routinely in practice should be developed and DSD should be included in prognostic models of health care.

Keywords: Delirium-superimposed dementia; delirium; dementia; elderly; institutionalization; mobility; mortality.

Fig. 1

Distribution of mobility dependence at discharge and at follow-up according to the cognitive diagnosis (no delirium no dementia, delirium alone, dementia alone, DSD). In this description are excluded the 239 patients who died in the year after the discharge. Mobility dependency was defined using the Barthel Index mobility subitem score <15.

Fig. 2

Proportion of patients with mobility impairment at rehabilitation discharge and at 1-year follow-up according to the cognitive diagnosis (none, delirium, dementia, DSD). The greatest improvements in mobility are seen in the delirium and DSD groups. The negative effect of DSD on mobility dependence is sustained at 1-year follow-up.