Background: Delirium is a common geriatric syndrome, with a prevalence of between 15-70% among older long-term care residents. It is associated with adverse outcomes, and its onset may prove imperceptible to health professionals. Few studies in institutionalized older people have analyzed the predictors of delirium. Objective: The aim of the present study was to identify delirium predisposing and triggering factors, and develop a predictive model. Methods: A cohort trial-nested case-control study covering a period of 12 consecutive months (April 2015 -March 2016) was carried out. Predisposing and triggering episodes of delirium were recorded. Results: A total of 443 older persons were recruited, with a mean age of 85.73 (6.72) years and female predominance (78.3%; n = 374). The incidence of older people with delirium was 18.7% (n = 83). Dementia was the predisposing factor with the highest predictive capacity (OR = 2.74 [1.49-5.04]). In the presence of dementia, falls (OR = 2.45 [1.49-3.69]), neuroleptics ) and anticholinergic drug use ) were identified as triggering factors. The area under the curve (AUC) was 0.72 (95%CI: 0.66-0.78). Conclusions: Our findings suggest that interventions targeted to potentially preventable triggering factors could avoid the onset of delirium in older people with dementia. Knowledge of the predictive factors of delirium facilitates the screening of older people at increased risk, thereby allowing mental health service providers to prevent and identify the onset of a delirium episode. The decrease in delirium predictive factors should lead to a direct reduction in the occurrence of delirium and its consequences.

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The prevalence of delirium among elderly subjects admitted to nursing homes was 60.7%. Infections (with the exception of urinary tract infections), dementia, anticholinergic drug use, depression and urinary incontinence were predictive of the presence of delirium.