Research Article: Association between delirium superimposed on dementia and mortality in hospitalized older adults: A prospective cohort study

Date Published: March 28, 2017

Publisher: Public Library of Science

Author(s): Thiago J. Avelino-Silva, Flavia Campora, Jose A. E. Curiati, Wilson Jacob-Filho, Bruce L. Miller

Abstract: BackgroundHospitalized older adults with preexisting dementia have increased risk of having delirium, but little is known regarding the effect of delirium superimposed on dementia (DSD) on the outcomes of these patients. Our aim was to investigate the association between DSD and hospital mortality and 12-mo mortality in hospitalized older adults.Methods and findingsThis was a prospective cohort study completed in the geriatric ward of a university hospital in São Paulo, Brazil. We included 1,409 hospitalizations of acutely ill patients aged 60 y and over from January 2009 to June 2015.Main variables and measures included dementia and dementia severity (Informant Questionnaire on Cognitive Decline in the Elderly, Clinical Dementia Rating) and delirium (Confusion Assessment Method). Primary outcomes were time to death in the hospital and time to death in 12 mo (for the discharged sample). Comprehensive geriatric assessment was performed at admission, and additional clinical data were documented upon death or discharge. Cases were categorized into four groups (no delirium or dementia, dementia alone, delirium alone, and DSD). The no delirium/dementia group was defined as the referent category for comparisons, and multivariate analyses were performed using Cox proportional hazards models adjusted for possible confounders (sociodemographic information, medical history and physical examination data, functional and nutritional status, polypharmacy, and laboratory covariates). Overall, 61% were women and 39% had dementia, with a mean age of 80 y. Dementia alone was observed in 13% of the cases, with delirium alone in 21% and DSD in 26% of the cases. In-hospital mortality was 8% for patients without delirium or dementia, 12% for patients with dementia alone, 29% for patients with delirium alone, and 32% for DSD patients (Pearson Chi-square = 112, p < 0.001). DSD and delirium alone were independently associated with in-hospital mortality, with respective hazard ratios (HRs) of 2.14 (95% CI = 1.33–3.45, p = 0.002) and 2.72 (95% CI = 1.77–4.18, p < 0.001). Dementia alone did not have a significant statistical association with in-hospital mortality (HR = 1.69, 95% CI = 0.72–2.30, p = 0.385). Finally, while 24% of the patients died after discharge, 12-mo mortality was not associated with dementia or delirium in any of the diagnostic groups (DSD: HR = 1.15, 95% CI = 0.79–1.68, p = 0.463; delirium alone: HR = 1.05, 95% CI = 0.71–1.54, p = 0.810; dementia alone: HR = 1.19, 95% CI = 0.79–1.78, p = 0.399). Limitations to this study include not exploring the effects of the duration and severity of delirium on the outcomes.ConclusionsDSD and delirium alone were independently associated with a worse prognosis in hospitalized older adults. Health care professionals should recognize the importance of delirium as a predictor of hospital mortality regardless of the coexistence with dementia.

Partial Text: Delirium is an acute disturbance of the mental state that has a fluctuating nature and is characterized by inattention and cognitive impairment. Its occurrence depends on an intricate relationship between predisposing and precipitating factors, which amount to more than 60 characteristics associated with delirium [1]. Older adults who have three or more of these characteristics have a 60% higher risk of developing delirium. Advanced age, preexisting dementia or cognitive impairment, functional dependence, and visual impairment are particularly relevant risk factors in this context [2].

We included 1,409 hospitalizations, representing 1,204 patients (Fig 1). Participants were predominantly very old, female, and from middle- to low-income groups (Table 1). Most admissions were referred from the emergency department, and nearly half of these cases waited at least 48 h before being transferred to our unit. Median length of hospital stay was of 15 d (interquartile range [IQR] = 9; 26). The median Charlson Comorbidity Index score was 3 (IQR = 1; 5).

In our cohort of acutely ill hospitalized older adults, we observed that DSD occurred in 26% of admissions. Approximately one in three of these admissions resulted in death during hospitalization, with a cumulative mortality of 57% at 12 mo. The high frequency of delirium and dementia and the elevated mortality rates are consistent with data reported in the literature [2,17]. We found that delirium in the absence of dementia and DSD were both associated with increased hospital mortality compared to those with no delirium/dementia. In contrast, we did not find statistically significant associations between delirium, dementia, or DSD and 12-mo mortality after adjustment for confounding factors. Other factors demonstrated to have prognostic importance in our cohort were age, admission from an emergency department or intensive care unit, functional dependency, malnutrition, cancer, reduced GFR, and hypoalbuminemia.



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