Clinical characteristics and risk factors of delirium in demented and not demented elderly medical inpatients

Objectives: to evaluate the differences in clinical characteristics and risk factors of delirium in elderly medical inpatients according to the presence or not of dementia. Design: cross-sectional, observational study. Setting: acute medical care unit (ACU) of a general hospital. Participants: 330 patients aged 65 and older consecutively admitted on a 24-week period. Measurements: Functional status, cognitive abilities, severity of acute illness (Acute Physiology, Age and Chronic Health Evaluation (APACHE II) score), Confusion Assessment Method (CAM), Delirium Rating Scale (DRS) and One Day Fluctuation Scale (ODFS). Results: patients with delirium represent 19.1% of the sample, 41.0% of which had also dementia. Hyperactive form of delirium was 41.0%; hypoactive 11.0% and mixed 48.0%. In non demented patients, the delirious patients showed higher APACHE II score, more severe functional decline, poorer cognitive status respect to not delirious. In demented patients no differences were found in APACHE II score and cognitive status among delirious and not delirious subjects. In this group, functional decline (p=.012), acute infection (p=.007), psychotropic drugs use (p=.028) and severe hypoalbuminemia (p=.036) represented risk factors for the onset of delirium. Demented patients had higher perceptual disturbances (p=.040) and less severe delusions (p=.001), while total DRS score do not differs in the two groups. According to ODFS, delirium episode was more fluctuating in patients with dementia. Conclusion: clinical characteristics and risk factors of delirium are different in demented and not demented elderly inpatients. Patients with dementia are vulnerable to delirium at lower levels of medical acuity than non-demented patients.