Predisposing and precipitating factors for delirium in a frail geriatric population

Abstract

Objective

The aim of this study was to assess the possible predisposing aetiologic and short-term precipitating factors for delirium in acutely ill hospital patients with a heavy burden of comorbidities and medications.

Methods

Eighty-seven consecutive patients with acute delirium admitted to a general medicine unit were thoroughly examined, and the predisposing and precipitating factors of their delirium were assessed.

Results

In this population, an average of 5.2 predisposing factors and 3.0 potential precipitating factors for delirium was revealed, meaning an average of over eight possible aetiological causes for each patient. The most common precipitating factors were infections (n=72), metabolic abnormalities (n=52), adverse drug effects (n=41), and cardiovascular events (n=38). In addition, a number of very rare conditions were diagnosed after thorough assessments.

Conclusion

Geriatric patients with acute delirium typically present with several concomitant predisposing factors for delirium exposing them to high vulnerability for the syndrome. In most patients, a number of possible etiological causes for delirium can be identified after a careful assessment, but their true pathogenetic pathway to the syndrome is unclear.

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.