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common adverse events in older people:

       Hospital‐acquired infection (in older patients, notably aspiration pneumonia and catheter‐associated infections)

       Adverse drug events

       Venous thromboembolism

       Procedure‐related complications

As with other adverse events in the hospital, at first glance, the incidence of adverse drug events seems to increase with age, but there is some evidence that they are directly related to complexity and comorbidity rather than age alone. Recent studies have estimated the incidence of adverse drug events in older people in the hospital to be between 31.9 and 37%.³⁴ As with all estimates of hospital‐associated risks, this figure depends very much on the definitions and methodologies used. Nevertheless, even when relatively strict definitions are used, adverse drug events are the most common adverse events to affect hospitalized patients of all ages.³⁵

      People over 60 are the highest users of medications, receiving 59% of dispensed prescriptions in the UK.³⁶ Polypharmacy is an important issue – one‐fifth of people age 70 years take five or more medications.³⁷ Virtually all older patients who are admitted to the hospital are given drug treatment of some description. It would be unusual for an older patient not to have been taking any medications prior to admission or for these not to have changed in some way by the time of discharge.

Adverse drug events are also a significant cause of hospital admission in older people (estimated at 6.5% of admissions, with a median length of stay of 8 days³⁸). Furthermore, patients admitted because of an adverse drug event have a significant chance (17.7%³⁹) of subsequent readmission due to further adverse drug events. Box 11.2 shows the common types of medication‐related problems that may occur at different stages of the hospital admission process in an older person.

      Outside the hospital, the highest users of medications are care home residents. A recent study in the UK showed that the incidence of medication errors in nursing home residents was as high as 69.5%.⁴⁰ The categories of error found were similar to those in Box 11.2 – they included prescribing, monitoring, dispensing, and administration errors. The underlying causes of the errors in both hospitals and care homes relate to common underlying patient safety themes: system failures, individual errors, communication problems within and between healthcare teams and the patient, and assessment or diagnostic skills and procedures not tailored to the individual.

      Certain categories of drugs are more problematic than others for older people, notably anticoagulants, opiates, and other centrally acting medications. Several efforts have been made to identify groups of medications that pose a particular risk so that they can be more easily avoided in this population, such as those categories of drugs included in the Beers criteria.⁴¹ The fact that common treatments such as oxygen and intravenous fluids should be treated the same way as other drugs is sometimes forgotten, but these are potentially dangerous treatments (particularly for older patients) and should be administered with due caution. The physiological changes associated with normal ageing and the pathological changes associated with disease processes common among older people in the hospital all impact the risks associated with giving medications to this population. These changes have effects on the pharmacokinetics and pharmacodynamics of virtually all medications.

      Frail elderly people are rarely included in large pharmaceutical trials, which in turn may result in harm because findings from clinical trials involving younger patients may be incorrectly extrapolated to older patients. The changes that occur with age also have practical implications in terms of drug regimens, administration, and concordance; for example, swallowing difficulties, arthritis, and cognitive or visual impairment need to be taken into consideration when prescribing and administering drugs to these complex patients.

      As with all patient‐safety issues in older people, adverse drug events do not occur in isolation – they are closely linked to the geriatric syndromes in both cause and effect. The unique characteristics of the frail elderly again play a part here. Because of the frequently nonspecific ways in which adverse drug events present in these patients (often in the form of the geriatric syndromes described above, particularly delirium or falls), they often go unrecognized — and rather than the causative agents being stopped, more medications are added, causing further adverse effects. This can lead to a vicious circle known as the prescribing cascade.⁴²

      Implications

The undoubtedly higher rate of adverse events in older people has obvious implications financially and for service provision. We must also consider the inescapable implications of the ageing population. By 2025, the number of people in the UK over age 85 will increase by two‐thirds; people over 65 account for 60% of acute hospital admissions and 70% of bed days in National Health Service (NHS) hospitals. Ensuring patient safety and high‐quality care for the growing number of older patients in healthcare systems might be seen as a battle against the inevitable consequences of illness and age, combined with the negative outcomes of preventable geriatric syndromes and adverse effects of treatments and interventions.

Box 11.2 Common types of medication‐related problems in older people in the hospital.

      Why are older people more susceptible to healthcare‐associated harm than younger patients?

      The causes of harm to patients are complex and may lie in individual error, process factors, organizational or cultural issues, or wider system problems. In this section, we address a number of issues that are particularly critical in the care of older people.

      The effects of comorbidity and frailty

      As major international studies have shown, adverse events are not associated with age alone but rather with comorbidity, complexity, and frailty. Comorbidity is commonplace among the elderly: 98% of people over the age of 65 in one primary care population had multiple chronic medical conditions.⁴³ For patients, this leads to complex care needs, interacting medical conditions, and polypharmacy – all of which make them more vulnerable to poorer outcomes in general, such as increased mortality and length of hospital stays. In this group, acute illness is usually associated with exacerbations of multiple coexisting chronic diseases, which interplay to produce complex physiological, cognitive, and functional consequences. Of course, there is a great deal of inter‐individual heterogeneity in the way in which these complexities manifest themselves. It follows that acute illness leading to hospitalization in such individuals is rarely as straightforward as it might be in a younger, fitter patient, and hence more healthcare‐associated harm can occur. A review of dementia patients in acute hospitals revealed significant adverse events including falls, functional decline, delirium, increased length of stay, and even mortality.⁴⁴ There were many contributory factors including inadequate assessment and treatment, unnecessary interventions, and limited resources.

      Frailty can be, but is not always, associated with the latter stages of chronic illnesses. Definitions vary, but frailty is understood to be a clinical syndrome in its own right, associated with loss of reserve in multiple organs and a clinical phenotype of generalized weakness, weight loss, exhaustion, and immobility.⁴⁵ This loss of reserve leads to the frail individual being less able to withstand illness and hospitalization than those without the condition.

The interaction between older people with multiple comorbidities, complexity, and frailty with the healthcare system is often complicated by the fact that illness presents

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