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Nursing Research:
doi: 10.1097/NNR.0000000000000004
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Factors Associated With Onset of Delirium Among Internal Medicine Inpatients in Spain

Díez-Manglano, Jesús; Palazón-Fraile, Claudia; Diez-Massó, Fabiola; Martínez-Álvarez, Rosa; Del Corral-Beamonte, Esther; Carreño-Borrego, Pilar; Pueyo-Tejedor, Pilar; Gomes-Martín, Javier

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Author Information

Jesús Díez-Manglano, MD, PhD, is Staff Doctor, Internal Medicine Department, Hospital Royo Villanova, and Main Researcher of the Research Group on Comorbidity and Polypathology, Aragón Health Sciences Institute, Zaragoza, Spain.

Esther Del Corral-Beamonte, MD, is Staff Doctor, Internal Medicine Department, Hospital Royo Villanova, Zaragoza, Spain.

Claudia Palazón-Fraile, RN, is Staff Nurse; Fabiola Díez-Massó, RN, is Staff Nurse; Rosa Martínez-Álvarez, MD, PhD, is Staff Doctor; Pilar Carreño-Borrego, RN, is Staff Nurse; Pilar Pueyo-Tejedor, RN, is Staff Nurse; Javier Gomes-Martín, MD, is Resident Doctor, Internal Medicine Department, Hospital Royo Villanova, Zaragoza, Spain.

Accepted for publication August 20, 2013.

The authors would like to recognize and thank the researchers of the Intervención Mínima en Pacientes Ingresados en Medicina Interna study: Patricia Al-Cheikh-Felices; Susana Alcubierre-Iriarte; María Jesús Arnal-Longares; Julia Barranco-Usón; Esperanza Bejarano Tello; Cristina Fernández-Jiménez; Juan Carlos Ferrando-Vela; Vanesa Garcés-Horna; María Soledad Isasi de Isasmendi-Pérez; María Pilar Lambán-Aranda; María Cristina Landa-Santesteban; Pablo Martínez-Rodés; María Pilar Moreno-García; Eulalia Munilla-López; María Jesús Pardo-Díez; Santiago Alfonso Rubio-Félix; Rogelio Serrano Lázaro; María Sevil-Puras; Sofía Terrén-Portolés; and Carla Toyas-Miazza, Internal Medicine Department, Hospital Royo Villanova, Zaragoza, Spain.

The authors have no funding or conflicts of interest to report.

Corresponding author: Jesús Díez-Manglano, MD, PhD, Hospital Royo Villanova, Avda San Gregorio n° 30, 50015 Zaragoza, Spain (

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Delirium increases mortality and length of stay among hospital inpatients. Little is known about the incidence of delirium among inpatients receiving care in internal medicine nursing units in Spain.


The aim of this study was to estimate frequency of delirium onset among internal medicine inpatients and identify factors associated with delirium onset using nursing records and administrative databases.


Retrospective cohort study of 744 patients hospitalized in an internal medicine department in October 2010 and January, May, and October 2011. Data concerning occurrence of delirium, age, gender, living in a nursing residence, Barthel Index of activities of daily living, Norton scale for pressure ulcer risk, intravenous fluid therapy, urinary catheterization, presence of pressure ulcers, major diagnostic category at discharge, length of stay, and mean weight in the diagnosis-related group were gathered for each patient. Backward stepwise logistic regression was used to identify factors associated with onset of delirium.


Ninety-seven (13%) patients experienced delirium. Factors associated with delirium were age (OR = 1.03, 95% CI [1.01, 1.06]), Barthel Index (OR = 0.99. 95% CI [0.98, 0.99]), and urinary catheterization (OR = 2.00, 95% CI [1.19, 3.68]).


Increased age and presence of a urinary catheter were associated with increased onset of delirium, whereas higher levels of independence in activities of daily living were protective.

Delirium is a disturbance of consciousness and cognition with a rapid onset, fluctuating course, and exogenous cause (Robertsson, 2002). Among medical inpatients admitted in an acute care hospital, the occurrence of delirium has been reported to vary between 11% and 42% (Siddiqi, House, & Holmes, 2006) and has shown associations with older age, nervous system diseases, dehydration, infections, and polypharmacy. Delirium is a complication that diminishes patient functional ability (Moller et al., 1998) and is associated with mortality (McCusker, Cole, & Abrahamowicz, 2002; Leslie et al., 2005; Witlox et al., 2010), longer length of stay (McCusker, Cole, & Dendukuri, 2003; Stevens, de Moore, & Simpson, 1998), and number of readmissions (Inouye, Rushing, & Foreman, 1998). It has also been associated with a higher risk of subsequent dementia and with institutionalization (Witlox et al., 2010).

Nurses are in contact with a patient 24 hours a day, and nursing care is crucial for the prevention and early detection of delirium. They note in their records any variations in patient physical and mental condition as well as types of care patients receive.

The hypothesis is that certain hygiene procedures and care during hospitalization can be risk factors for the onset of delirium. This study aimed to determine the factors associated with the onset of delirium within an internal medicine department, using information in nursing records and administrative databases.

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The study was conducted in Royo Villanova Hospital in Zaragoza, Spain. The hospital attends a population of 200,000 people. There are two internal medicine nursing units, each with 30 beds. In 2011, there were 2,166 admissions, and 96% came from the emergency department. The units were similar except that a simple reminder system called Intervención Mínima en Pacientes Ingresados en Medicina Interna was implemented on one of the units in October 2010. Intervención Mínima en Pacientes Ingresados en Medicina Interna is a simple reminder intervention designed to reduce the duration of urinary tract catheterization and intravenous fluid therapy. Twice a week, in the morning staff meeting, a reminder is given to remove the bladder indwelling catheters, stop intravenous fluid therapy, monitor the appearance of pressure ulcers, and detect early the occurrence of delirium.

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Data were obtained retrospectively using nursing records and the administrative database. Every patient admitted to one of the two nursing units of the internal medicine department during the months of October 2010, January 2011, May 2011, and October 2011 was included. At admission, a nurse interviewed all patients or their caregivers to check functional and mental status. For each patient, data concerning age, gender, living at home or in nursing residence, ability to carry out basic daily living tasks, risk of presenting pressure ulcers, occurrence or onset of delirium during hospitalization, major diagnostic category at discharge, length of stay, and mean weight in the diagnosis-related group (DRG) were gathered. The Barthel Index (Mahoney & Barthel, 1965) was used to measure ability to carry out basic daily living tasks in 10 areas: feeding, bathing, dressing, grooming, bladder control, bowels control, toilet use, transferring, moving on level surfaces, and walking up and down stairs. BI scores range between 0 and 100: the higher the score, the more independent the person. The risk of developing pressure ulcers was measured by the Norton scale (Norton, McLaren, & Exton-Smith, 1979), which reflects five parameters: physical condition, mental condition, activity, mobility, and incontinence. The scale scores range between 0 and 20: the lower the score, the higher the risk. Delirium was scored “present” whenever the words “delirium” or “confusion” were expressly mentioned in the nursing records or administrative database. The study was approved by the Clinical Investigation Ethics Committee of Aragón.

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Statistical Analysis

A descriptive analysis of the sample was carried out using medians and interquartile ranges for quantitative variables and percentages for categorical ones. Comparisons between patients with and without delirium were made by applying the Mann–Whitney test for the former and the chi-squared test for the latter. Univariate and multivariate logistic regression analyses were carried out to assess the association of each variable with the occurrence of delirium. In the univariate analysis, variables with a difference between patients with and without delirium were included. A backward stepwise multivariate logistic regression model was estimated that incorporated all variables significant at p <; .10 in a univariate analysis. A nominal type 1 error rate of .05 was used in the multivariate model.

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There were 768 admissions during the periods of the study. In 24 cases, data could not be gathered, so eventually 744 (96.9%) were included (Figure 1). Patient characteristics are presented in Table 1. The mean age of patients was 74.5 (SD = 16) years, and 389 (52%) were women. Ninety-seven (13%) patients experienced delirium during their hospitalization. The prevalence of delirium was not different among different months (12.0%, 13.1%, 14.1%, and 12.9%; p = .95).

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Factors Associated With Delirium Onset

Table 2 summarizes the results of the univariate and multivariate logistic regression analyses. In the univariate analysis, living in a nursing residence, a lower Barthel Index (higher degree of dependence), a lower score on the Norton scale (higher risk of pressure ulcers), urinary catheterization, use of intravenous fluid therapy, and development of pressure ulcers were associated with the onset of delirium. Respiratory diseases were positively associated, and digestive diseases were negatively associated with the onset of delirium.

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In the multivariate analysis, only age, Barthel index, and urinary catheterization were associated with the onset of delirium during hospitalization (Table 2). Intravenous fluid therapy lasted longer for patients who experienced delirium (M = 6 days and SD = 5 days vs. M = 3 days and SD = 5 days; p <; .001). A similar trend was seen for the duration of urinary catheterization, but the difference was not statistically significant (M = 6 and SD = 7 vs. M = 5 and SD = 7; p = .07).

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Mortality, Length of Stay, and DRG Weight

Patients who experienced delirium died during hospitalization more frequently (20.6% vs. 10.8%, p = .006). Their average stay was longer (M = 9 days and SD = 10 days vs. M = 7 days and SD = 8 days; p = .007), and their admission DRG weight was higher (M = 1.88 and SD = 1.23 vs. M = 1.37 and SD = 1.16; p <; .001).

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The study shows that 13% of internal medicine patients suffer delirium during their hospitalization.

On the basis of nursing records, the study shows that 13% of internal medicine patients experience delirium during their hospitalization and that age, Barthel Index, and urinary catheterization are independently associated with its onset.

In their systematic review of 42 worldwide cohort studies on inpatients, Siddiqi et al. (2006) observed that the occurrence of delirium ranged from 11% to 42%. In Spain, studies on the prevalence of delirium are rare and show frequencies between 15% and 18% (Bernabeu-Wittel et al., 2010; Lázaro, Marcos, Cirera, & Pujol, 1995). A similar prevalence was also observed in this study. Despite the dimension of the problem, neither the prevalence nor the occurrence of delirium seems to have decreased over the years.

Patients in internal medicine departments are usually aged and frequently experience more than one disease. In Spain, a recent study showed that the mean age of patients admitted to internal medicine nursing units of acute care hospitals has increased by 19.3 years over the last 20 years (Casademont, Francia, & Torres, 2011). In other studies, the mean age was between 70 and 72 years, and the average number of diagnosis per episode was 5.4 (Barba Martín et al., 2009; de San Román y de Terán & Guijarro Merino, 2006). In this study, the mean age of patients was above the one observed in the analysis of the basic minimum collection of data of Spanish Internal Medicine Services and that of American studies (Everett, Uddin, & Rudloff, 2007). Given the progressive aging of the population, delirium may become an epidemic affecting hospitalized or institutionalized patients, with the ensuing increase of mortality and economic expenses and a corresponding deterioration of the quality of life of patients and caregivers.

Some multicomponent interventions have proved effective in preventing the onset of delirium in elderly inpatients (Inouye et al., 1999). However, once delirium had occurred, intervention was less effective. Therefore, the most advisable strategy is to take proactive steps against risk factors associated with it. A significant find in this study was the fact that urinary catheterization is independently associated with the onset of delirium. Bladder catheters were already associated with the appearance of urinary tract infections, and yet, it is still commonly performed, often unnecessarily (Gokula, Hickner, & Smith, 2004). Its association with delirium remains widely unacknowledged, albeit, it was described years ago (Inouye & Charpentier, 1996; Van Rompaey et al., 2009). Few prospective studies assess the association of urinary catheterization with a new onset of delirium (Inouye & Charpentier, 1996). However, strategies seeking to improve patient mobility that included restricted urinary catheterization have been associated with a lower occurrence of delirium (Inouye, Bogardus, Williams, Leo-Summers, & Agostini, 2003; Inouye et al., 1999). In this study, average duration of urinary catheterization was about 1 day longer in patients with delirium (the difference was not statistically significant). Nevertheless, before proceeding to urinary catheterization, it is prudent to assess the risk of delirium and the need for catheterization. Elimination of urinary catheters as soon as possible may help to decrease the onset of delirium, but more studies are needed.

It was found that intravenous use of fluids was more frequent and lasted longer in patients with delirium. It is known that delirium increases with the number of perfusions (Van Rompaey et al., 2009). Intravenous therapy implies mobility restrictions for many patients, especially the older adults, and immobility is associated with the onset of delirium.

Multiple other factors contribute to delirium. In contrast with geriatric patients with hip fracture (Chrispal, Mathews, & Surekha, 2010), we found that inability to carry out basic daily living activities, measured with the Barthel Index, was associated with delirium. This finding is in line with other reports in medical inpatients (McCusker, Cole, Dendukuri, & Belzile, 2004). This finding can be explained because lower scores in Barthel Index are associated with immobility. In the older adults, urinary catheterization is a cause of immobility, and immobility also predisposes to pressure ulcers. In this study, pressure ulcers were more frequent in patients with delirium.

Reliance on mention of “delirium” or “confusion” in nursing notes or administrative data as an indicator of delirium was a limitation of this study. Still, the findings showing occurrences of delirium at 13% of admissions is consistent with other studies that used standardized assessment approaches. In a study based on symptoms recorded by nurses using the Confusion Assessment Method (Inouye et al., 1990), the rate of delirium was 12% (Bourdel-Marchasson et al., 2004), and another study conducted by researchers using clinical interviews noted a 15% rate (Cameron, Thomas, Mulvihill, & Bronheim, 1987). At any rate, it cannot be excluded that, in this study, delirium might have been underrecognized, as some studies conducted on doctors (Gustafson, Brannstrom, Norberg, Bucht, & Winblad, 1991) and nurses (Inouye, Foreman, Mion, Katz, & Cooney, 2001) have shown to be sometimes the case. Considering that the Confusion Assessment Method scale is readily applicable, its use both in emergency rooms, where the first contact of patients in the hospital often takes place, and in internal medicine departments, especially on those patients who might require catheterization for diagnostic or therapeutic reasons, may be warranted.

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delirium; geriatrics; hospitalization; nursing

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