Causes and prognosis of delirium in elderly patients admitted to a district general hospital

Age and Ageing, Nov, 1997 by James George, Sheena Bleasdale, Steven J. Singleton

Introduction

Delirium (acute confusional state) is a common condition in old age and has a high mortality [1]. If the patient survives the acute stage, the longer-term outlook for delirium is said to be good [2]. However, a recent meta-analysis from psychiatric units and tertiary hospitals, mainly in the USA [3], contradicts this belief and suggests that the long-term prognosis is very poor with a high late, as well as early, mortality and a high likelihood of institutionalization. We report a case-control study of the causes and prognosis of delirium in elderly patients admitted to a typical district general hospital in the UK.

Methods

For 1 year a research nurse (S.B.) was employed to screen and follow-up all elderly patients (over 65 years) admitted to Cumberland Infirmary, Carlisle, with confusion as part of their presenting complaint. Cumberland Infirmary is a 376-bed district general hospital providing all main acute services to a population of approximately 190 000.

All relevant wards were contacted each week and asked to report all patients with confusion. All patients referred were assessed and patients satisfying the American Psychiatric Association's Diagnostic and Statistical Manual III criteria for delirium [4] (Table 1) were included in the study. Patients who were known to be terminally ill were excluded.

Table 1. American Psychiatric Association's Diagnostic and Statistical Manual III criteria for delirium

A Clouding of consciousness (reduced clarity of awareness of the environment), with reduced capacity to shift, focus and sustain attention to environmental stimuli

B At least two of the following:

1 Perceptual disturbance: misinterpretations, illusions or hallucinations

2 Speech that is at times incoherent

3 Disturbance of the sleep-wakefulness cycle, with insomnia or daytime drowsiness

4 Increased or decreased psychomotor activity

C Disorientation and memory impairment

D Clinical features that develop over a short period of time (usually hours to days) and tend to fluctuate over the course of a day

E Evidence, from the history, physical examination or laboratory tests, of a specific organic factor judged to be aetiologically related to the disturbance

The diagnosis of patients with delirium was confirmed by a consultant physician (J.G.). Mental function was assessed using the Abbreviated Mental Test Score [5]. The likely cause of delirium was ascertained using the criteria established by Francis et al. [6]--i.e. that the confusion appeared related to an observed factor which is known to cause confusion and improvement followed either treatment or cessation of the factor responsible. Delirious patients were followed through-out their hospital admission in order to determine the likely cause.

The patients were also examined for visual and hearing impairment as these are thought to be contributory factors [7]. Patients were identified as being visually impaired if their visual acuity was less than 6/18 in the better eye and hearing impaired if unable to hear a whispered voice at 15 cm [8]. All patients with delirium were then followed-up and assessed further at 6 and 12 months.

Control patients who were in hospital at the same time and on the same wards, but had no symptoms of confusion at any time during their hospital admission, were selected and also examined and followed-up.

Results

One hundred and seventy-one patients with delirium were identified and followed-up (78 men and 93 women). The age range was 65-98 (mean 81) years. One hundred and fifty controls were approached, of whom 95 agreed to take part in the study. The controls included 58 women and 37 men, age range 68-92 (mean 80) years.

The identified causes of delirium are given in Table 2 and the controls and patients are compared in Table 3. The control patients had similar medical diagnoses to the patients with delirium and were closely matched for age and sex. By far the commonest cause of delirium was found to be infection, particularly chest and urinary infections. Forty-two patients (25%) had multiple potential causes of the delirium.

Table 2. Causes of delirium in 171 patients(a)

                                         No. of
Cause                                    cases        %

Infection                                 73         34
  Chest                                   40         --
  Urinary                                 25         --
  Other                                    8         --
Stroke                                    24         11
Drugs(b)                                  24         11
Myocardial infarction                     11          5
Fractures                                 10          5
  Hip                                      7         --
  Other                                    3         --
Carcinoma                                 10          5
Fluid and electrolyte imbalance            9          4
Heart failure                              8          4
Diabetes (hypo- or hyperglycaemia)         7          3
Peripheral vascular disease/gangrene       6          3
Alcohol withdrawal                         6          3
Gastrointestinal bleed                     5          2
Respiratory failure                        5          2
Pulmonary embolus                          4          2
Anaemia                                    4          2
Perforation of duodenal ulcer              2          1
Subdural haematoma                         2          1
Brain tumour                               1        0.5
Miscellaneous                              6          3
Total                                    217         --