**3.1.4 Severe, traumatic or systematic illnesses**

Medical comorbidities such as burns (Palmu, 2011), cancer (Bond et al., 2011), cardiovascular disease (Branco et al., 2011), and alcoholism (Pompei et al., 1994) are among the predisposing factors for delirium. Sensory impairments like visual impairment and functional dependence also predispose individuals to delirium (Burns et al., 2004). In a study investigating a multifactorial model of delirium etiology, a predictive model was formed and 4 predisposing factors were identified for delirium: vision impairment, severe illness, cognitive impairment and BUN/creatinine ratio of 18 (Inouye, 1999).

Having a severe illness and staying in intensive care unit are also predisposing factors for delirium. Delirium has been reported in up to 80% of critically ill patients (Ouimet et al., 2007). Delirium is an independent predictor of adverse intensive care unit outcomes, including increased risk of death, longer hospital stay, and higher costs (Ely et al., 2004; Milbrandt et al., 2004; Thomason et al., 2005).
