Background: Delirium superimposed on dementia (DSD) is highly prevalent and associated with high mortality among hospitalized elderly patients, yet little is known about the effect of DSD on midterm mortality. The purpose of this study was to assess 12-month survival in patients with DSD and matched groups with dementia alone, delirium alone, or neither delirium nor dementia.
Methods: Among 1278 consecutively admitted elderly participants (aged > or =65 years) to our Rehabilitation Unit between January 2002 and May 2005, four matched samples of 47 participants each (DSD, dementia alone, delirium alone, or neither delirium nor dementia) were selected. Matching was based on age, gender, and reason for admission. Postdischarge 12-month survival was assessed in the four groups with Kaplan-Meyer analysis and compared with Cox proportional hazard regression models adjusted for confounders.
Results: Survival was significantly lower for DSD patients than for the other three groups. After adjustment for comorbidity and Barthel Index score before admission, patients with DSD had significantly higher mortality (hazard ratio, 2.3; 95% confidence interval, 1.1-5.5; p =.04) than did patients with neither delirium nor dementia.
Conclusions: Demented patients who experienced delirium during hospitalization had a more than twofold increased risk of mortality in the 12 months following discharge than did patients with dementia alone, with delirium alone, or with neither dementia nor delirium.