Original articlePredisposing and precipitating factors for delirium in a frail geriatric population
Introduction
The possible aetiological causes for delirium are known to be numerous, but only a few studies have systematically assessed them [1], [2], [3], [4]. The main focus in clinical delirium studies has been on its incidence and prevalence [3], [4], [5], [6], [7], symptom profile [8], [9], [10], [11], or outcome [4], [5], [6], [8], [12]. Most of these studies have not reported the exact definition of the etiologies, nor the diagnostic procedures behind the assessments. Consequently, the classification of different aetiological categories presented may be superficial. Comparisons are further hampered by a great variability of study populations, classifications of etiologies, criteria for delirium, and end points.
During the developmental process of the Diagnostic and Statistical Manual of Mental Disorders (DSM) by the American Psychiatric Association, the requirement for the aetiological cause for delirium has been changed. In its fourth edition (DSM-IV) [13], the criteria for delirium explicitly require evidence of an organic etiology to the syndrome.
Inouye et al. [14], [15] have divided the etiology of delirium into predisposing and precipitating factors, the former characterizing the person's vulnerability for the syndrome and the latter the actual “trigger” to initiate it. The most important predisposing factors for delirium are shown to be old age and cognitive decline [16]. Despite being sometimes arbitrary, this division is believed to be useful in understanding the possible aetiological pathways and mechanisms behind the syndrome. A minor precipitating factor may trigger delirium in a patient with major predisposing factors, such as very high age, multimorbidity, dementia, postoperative state, advanced cancer, or admittance to intensive care unit [15].
The aim of this study was to assess (1) the predisposing factors and (2) potential short-term precipitating factors for delirium among very old, acutely ill, hospital patients with multiple comorbidities and medications. This study was originally designed as a randomized, controlled intervention study to assess the effect of multicomponent geriatric intervention on outcome of delirium in a population of 174 geriatric patients with delirium [17]. In order to find the best possible treatment for each patient of the intervention arm (n=87), both the predisposing and precipitating factors of their delirium were thoroughly assessed by two skilled geriatricians. The findings of these intervention patients are presented here.
Section snippets
Methods
The study consisted of all consecutive patients ≥70 years admitted to general medicine services at one Helsinki City hospital from September 20, 2001, through November 24, 2002. The hospital serves 156 acute beds in the western area of Helsinki with a population of >100,000 inhabitants. Exclusion criteria included inability to obtain informed consent in two working days, admission from permanent institutional care, life expectancy less than 6 months, and refusal. Because all of the patients
Results
Mean age of the patients was 83.8 years. Of those, 26.4% suffered from prior dementia. Patients had an average of 5.6 (range 1–11) prior medical diagnoses at admission. The Charlson Comorbidity Index [24] also indicated a high number of comorbidities (Table 1). We found altogether 451 predisposing factors for delirium among these patients. All patients had several predisposing factors. Four in five were functionally dependent, 98% had multiple comorbidities, and 29% suffered from depression.
Discussion
Our study revealed a high number of potential predisposing and precipitating factors for delirium in an old, acutely ill, geriatric population. After the full geriatric assessment of this patient group known to be very vulnerable to delirium [27], [28], the syndrome in most cases was judged to be associated with several predisposing and precipitating factors.
The strength of our study is its pragmatic nature. We studied patients known to be extremely vulnerable to delirium [27], [28]. The number
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