Inappropriate prescribing in the older population

Current estimates state that there are 10 million people over the age of 65 years in the UK and this figure is expected to increase by 50% in the next 20 years. Closer inspection reveals that there are currently three million people over 80 years of age, a figure set to almost double by 2030.^1,2 The over 65 years population currently accounts for 65% of admissions to secondary care and the majority (70%) of bed days at any given time.³

PolypharmacyThere is currently no accepted singular definition of polypharmacy with many clinicians citing polypharmacy as the concurrent use of more than four medications, while one review article stated the use of more than six medications as a common cut off.⁴ Irrespective of the definition, polypharmacy is an endemic problem within older populations. In a large multinational study, it was found that 48% of patients in the UK receiving home care were taking six or more medications.⁵ Clearly, patients with multiple comorbidities may require the prescription of many medications, but the importance of the collective impact of polypharmacy on an individual patient basis cannot be overlooked, with polypharmacy contributing to an individual patient’s risk of falls, episodes of delirium, prescribing errors and hospital attendances as a result of adverse drug events (ADE). Pirmohamed et al estimated that up to 6.5% of all hospital admissions are related to an ADR, with the over 65s accounting for 50 to 65% of these admissions.^6,7 Studies have shown potentially inappropriate medications (PIMs) to be associated with delirium, gastrointestinal bleeding, falls and fractures,⁸ all of which carry high risk of morbidity and mortality. It has also been documented that polypharmacy at presentation is an important risk factor for increased length of stay for a given admission⁹ and cause of rehospitalisation.¹⁰  Inappropriate prescribing can be defined as €œthe prescription of medications where risk outweighs benefit, failure to use a safer alternative drug, the misuse of a drug including incorrect dosage and duration of treatment, use of drugs with significant drug€“drug and drug€“disease interactions and finally the omission of beneficial drugs.€¹¹ Multiple interlinked factors contribute to the complex decision making process undertaken when prescribing a drug and this is amplified in older, complex patients. Physiological, pharmacokinetic and pharmacodynamic changes associated with ageing mean that older people can be expected to both metabolise and respond to drugs differently to those in younger age groups. The general understanding of these processes is limited by the profession’s own understanding of the effects of ageing but also the skeletal way in which these processes are taught to medical and allied healthcare professionals. Comorbidity resulting in polypharmacy leads to the increased potential for drug€“drug and drug€“disease interactions which can contribute significantly to further morbidity and mortality. Even though modern medical practice is becoming more evidence-based, the majority of large drug trials do not proportionately represent older patients in their trial populations. At present, clinicians rely primarily on clinical judgement (implicit) when prescribing and reviewing medications for older complex patients. However, guidelines and screening tools are beginning to emerge into the clinical forum aimed at helping clinicians to predominantly avoid harmful prescriptions in the older population, but also consider prescribing useful and beneficial medications (explicit criteria). The two main forerunners in this field are the Beers’ criteria and the STOPP/START criteria (STOPP: screening tool of older persons’ prescriptions; START: screening tool to alert to right treatment). 

The American Beers’ criteriaThe American Beers’ criteria were first developed in the early 90s and comprised a list of 30 medications to be avoided in nursing home patients, irrespective of dose, indication and frequency of medication.¹⁴ The initial criteria were modified to include community populations shortly after their release but still failed to address omission of beneficial drugs, drug€“drug interactions and drug class duplication.¹⁵ The Beers’ criteria were subsequently updated in 2012 by the American Geriatric Society, listing 53 drugs divided into three categories of Potentially Inappropriate Medications (PIMs) or drug classes: those to avoid; those to avoid in certain diseases and syndromes and those to be used with caution. The updated Beers’ criteria also raises the point of considering non-pharmacological treatment when safer than the use of pharmacological treatment.8 A major limitation experienced with the Beers’ criteria was its inclusion of drugs specific to the American market and formularies thereby making aspects of it irrelevant to prescribing on an international scale. In addition, the evidence used in the development of the Beers’ criteria has, in some instances, been superseded by more up to date evidence that supports the use of some €œcontraindicated€ medications in the older population and conversely cautions against the use of others.¹⁶

The STOPP & START criteriaThe STOPP & START criteria were devised by a panel of 18 expert prescribers in older people from centres in the UK and Ireland in response to the limitations of the Beers’ criteria and more specifically prescribing outside the American market. Given the shortcomings of the Beers’ criteria, the panel focussed particularly on six principles: (i) the criteria should be as inclusive of common, significant instances of inappropriate prescribing as possible; (ii) the criteria should be developed through a systems based approach; (iii) the criteria should particularly consider drugs that may affect patients at risk of falls; (iv) opiates should be given special consideration; (v) duplication of drug classes should be illustrated; (vi) prescribing omission should be addressed. The result of the panel’s work is a validated screening tool comprising 68 STOPP systems based criteria and 22 START systems based criteria with good inter-rater reliability.¹⁶ There is little evidence comparing the use of these two tools given their differing markets. However, studies are starting to emerge in order to find the best use for each of these tools and how they can improve patient care. Work by Curtain et al demonstrated greater sensitivity of the STOPP/START criteria compared to the Beers’ criteria when used in an older community based population. They found that the Beers’ criteria identified 399 drug-related problems while the STOPP/START criteria identified 1032 via a greater number of descriptive terms. These figures were compared to the original pharmacists’ findings where 862 drug related problems were identified. They concluded that the STOPP/START criteria correlated most closely with the pharmacists’ findings, but that the criteria could be augmented by the use of the Beers’ (and other) available criteria.¹⁷In a small, Spanish, community based study, the STOPP criteria identified at least one inappropriate medication in 48% of patients in a nursing home while the Beers’ criteria identified potentially inappropriate prescribing in 25%. They also demonstrated a statistically significant correlation between then number of medications prescribed and the number of potentially inappropriate prescriptions.¹⁸ These findings add to the findings by O’Mahoney et al in which a direct comparison was made between the STOPP and Beers’ criteria in patients admitted to an acute hospital. They found that the STOPP criteria highlighted potentially inappropriate prescribing as causal or contributory factor in the acute admission in 11.5% of admissions, while the equivalent figure for the Beers’ criteria was 6%.¹⁶O’Mahoney et al extended their work to look at primary care populations in a study involving over 1,300 patient records. They showed that the STOPP criteria identified potentially inappropriate prescribing in 21.4% of patients whereas the Beers’ criteria identified inappropriate prescribing in 18.3%. They concluded that these tools serve to highlight the prevalence of inappropriate prescribing in primary care populations and demonstrate the usefulness of these tools, in particular the STOPP/START criteria in promoting effective prescribing.¹⁹

PrevalenceLooking further afield, a larger multi-centre study was carried out in six European university teaching hospitals involving the prospective collection of data from 900 patients to better identify the prevalence of inappropriate prescribing and also review the use of STOPP/START and Beers’ criteria. The prevalence of potentially inappropriate prescribing varied between countries, however the combined prevalence using the STOPP criteria was found to be 51.3%. The corresponding finding for the Beers’ criteria was 30.4%.²⁰ One US study looked at a population of older patients under psychiatry services. Although this was a small cohort of 29 patients, their data showed that significantly more potentially inappropriate prescriptions were identified by the STOPP criteria compared to the Beers’ criteria. Furthermore, on follow up of the recommendations made through the STOPP and Beers’ criteria, the number of falls within this cohort fell by 37.5%, demonstrating the potential clinical value of the use of these criteria.²¹The problem of inappropriate prescribing is a global one, as demonstrated by Vishwas et al who looked at data from 540 patients to compare the Beers’ and STOPP criteria for determining prevalence, specificity, sensitivity and predictors for potentially inappropriate prescribing. Interestingly, they highlight the different strengths of each tool which when used together provide a comprehensive review of prescriptions in the older patient. Of their cohort, the prevalence of potentially inappropriate prescribing was 24.6% for the Beers’ criteria and 13.3% for the STOPP criteria. This trend opposes the other studies discussed which demonstrate the STOPP criteria as being more sensitive. They concluded however that the Beers’ criteria are most useful when considering potentially inappropriate prescribing independent of diagnosis or condition compared to the STOPP criteria, which are most useful in the context of a known diagnosis or condition.²² This reiterates the findings of Curtain et al who concluded that the STOPP criteria are augmented by the concurrent use of the Beers’ criteria.

Conclusion In conclusion, these early studies looking at the use and implementation of the Beers’ and STOPP/START criteria have highlighted the prevalence of inappropriate prescribing in older populations and the importance of detecting and acting upon these prescriptions. Both tools require further development and arguably the STOPP/START criteria are the most valid in the context of medical practice in the UK. Neither tool is a substitute for clinical judgement or keeping the patient at the centre of care. Further larger studies are needed to compare these tools and establish their combined role in the field of clinical medicine but also to understand their individual uses and limitations. Finally, a greater understanding of the importance and impact of polypharmacy as a relevant factor contributing to hospital admissions is needed amongst those at the forefront of healthcare delivery.

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