Elsevier

The Lancet

Volume 364, Issue 9443, 16–22 October 2004, Pages 1421-1427
The Lancet

Articles
Prevalence of mental incapacity in medical inpatients and associated risk factors: cross-sectional study

https://doi.org/10.1016/S0140-6736(04)17224-3Get rights and content

Summary

Background

Although mental incapacity is becoming increasingly important in clinical practice, little information is available on its frequency in medical inpatients. We aimed to estimate the prevalence of mental incapacity in acutely admitted medical inpatients; to determine the frequency that medical teams recognised patients who did not have mental capacity; and to identify factors associated with mental incapacity.

Methods

Over an 18-month period, we recruited 302 consecutive acute medical inpatients. Participants were assessed with the MacArthur competence tool for treatment and by clinical interview. Cognitive impairment was measured by the mini-mental state examination.

Findings

72 (24%) patients were severely cognitively impaired, unconscious, or unable to express a choice and were automatically assigned to the incapacity group. 71 (24%) refused to participate or could not speak English. Thus, 159 patients were interviewed. Of these, 31% (95% CI 24–38) were judged not to have mental capacity. For the total sample (n=302), we estimated that at least 40% did not have mental capacity. Clinical teams rarely identified patients who did not have mental capacity: of 50 patients interviewed, 12 (24%) were rated as lacking capacity. Factors associated with mental incapacity were increasing age and cognitive impairment.

Interpretation

Mental incapacity is common in acutely ill medical inpatients, and clinicians tend not to recognise it. Screening methods for cognitive impairment could be useful in detecting those with doubtful capacity to consent.

Introduction

To ensure that consent to medical treatments and investigations is valid, a patient must be suitably informed, their consent must be given voluntarily, and the individual must have mental capacity to make the decision. In most jurisdictions, mental capacity is presumed—eg, in clinical practice, unless the patient shows very obvious signs of a mental or cognitive disorder, clinicians usually do not explicitly assess mental capacity. In the UK, several legal developments have taken place.1, 2 Whereas mental-health legislation in England and Wales is dealt with under separate statute,3 researchers have suggested that a revised Mental Health Act should be based on assessment of mental capacity.4, 5 In the USA, mental incapacity was one criteria for civil commitment under the American Psychiatric Association's model statute.6

Mental capacity is variously defined, but the proposed England and Wales legislation2 suggests that a patient does not have capacity if there is “an impairment of or disturbance in the functioning of brain or mind” that causes difficulty in decision making because the individual: (1) is unable to understand information relevant to the decision; (2) cannot retain the relevant information; (3) is unable to use this information as part of the decision-making process; or (4) cannot communicate the decision. Mental capacity is situation-specific, so an individual who does not have the capacity to make one decision could have capacity to make another, depending on the risks and benefits associated with the decision and its complexity.

When assessing mental capacity for a specific treatment decision, a clinician could be forced into making a binary decision about the presence or absence of capacity. However, the underlying processes that contribute to decision making are dimensional, and broad consensus suggests that these include understanding, appreciation, reasoning, and ability to express a choice about treatments.7, 8, 9 Various interviews and rating scales have been devised to assess capacity, many of which focus on these four (or similar) dimensions.10, 11, 12

Most samples previously studied for lack of capacity have been homogeneous groups of patients with stable and chronic medical or psychiatric disorders.9, 13, 14, 15, 16, 17 In studies of this type, individuals with organic disorders such as dementia or those with psychotic illness frequently lack capacity. Mental capacity might also be affected by other psychiatric disorders such as depression, but impairments are probably less frequent in this group.16 Impairments in capacity in heterogeneous groups such as acutely medically ill patients in hospital have been less extensively studied,12 yet they contribute a large population in which reduced capacity can be expected. We postulated that lack of capacity can sometimes be overlooked by clinicians, because many patients passively acquiesce to their doctor's advice and so difficulties remain undetected and might not be perceived by the clinical team. If a doctor doubts a patient's capacity, he or she might be reluctant to address this possibility explicitly, because to do so could have serious legal, ethical, and practical consequences.

We aimed to establish the prevalence of operationally defined incapacity in a random sample of general adult medical patients; the degree to which clinicians detect incapacity; and demographic and clinical associations of incapacity. We studied a mixed group of acutely ill medical inpatients, because this group of individuals will probably have high levels of cognitive impairment and severe medical illness that would impair capacity, and is a group in which critical treatment decisions generally have to be made quickly.

Section snippets

Participants

We obtained local research ethics committee approval for the study. We assessed the prevalence of incapacity in a mixed sample of adults (age 18 years or older) admitted non-electively under one medical firm to two acute general medical wards in a London teaching hospital over an 18-month period, who had any current diagnosis and treatment plan. Every week, we selected a sample of those eligible by numbering all consecutive ward admissions and using a random numbers table. Inpatients agreeing

Results

During the 18-month test period, 2000 patients were admitted to the participating wards, of whom 1606 were admitted for at least 48 h. 302 were included in the study. Of these, 143 were not interviewed: reasons included unconsciousness (n=14; 5%); unable to express a choice because of communication difficulties (n=19; 6%); and severe cognitive impairment (n=39; 13%). 16 patients (5%) could not communicate adequately in English to complete the interview and 55 (18%) refused to participate.

Table 1

Discussion

We have shown that lack of capacity to make treatment decisions is common in medical inpatients. The prevalences we reported are higher than those described in other samples of medical inpatients.12, 22 In one study,12 37% of patients who were assessed did not have capacity; however, that report was not a prevalence study because patients who the clinician was confident had capacity were excluded. Appelbaum and Grisso22 sampled people younger than 70 years who were being evaluated or treated

References (28)

  • T Grisso et al.

    Comparison of standards for assessing patients' capacities to make treatment decisions

    Am J Psychiatry

    (1995)
  • T Grisso et al.

    Assessing competence to consent to treatment

    (1998)
  • T Grisso et al.

    The MacArthur treatment competence study, III: abilities of patients to consent to psychiatric and medical treatments

    Law Hum Behav

    (1995)
  • T Grisso et al.

    The MacCAT-T: a clinical tool to assess patients' capacities to make treatment decisions

    Psychiatr Serv

    (1997)
  • Cited by (315)

    • Ethical challenges in obstetric emergencies in low- and middle-income countries

      2024, Best Practice and Research: Clinical Obstetrics and Gynaecology
    • Ethical Considerations Surrounding Patient Refusal of Emergent Aortic Surgery

      2024, Journal of Cardiothoracic and Vascular Anesthesia
    View all citing articles on Scopus
    View full text