A quantitative and qualitative analysis of potentially inappropriate prescribing in older adults

  • Sarah Baxter

Student thesis: Doctoral ThesisDoctor of Philosophy



Globally, population demographics are changing due to ageing. As people age, the prevalence of long-term conditions increases which gives rise to multimorbidity. Polypharmacy naturally accompanies multimorbidity and has many negative outcomes associated with it. When polypharmacy is prescribed appropriately, it is beneficial for the patient, leading to improved therapeutic outcomes. However, when polypharmacy is not prescribed appropriately, it can lead to potentially inappropriate prescribing (PIP). PIP occurs when the risk of an adverse event outweighs the intended clinical benefit of a medicine or when clinically indicated medicines are omitted. The overall aim of the research presented in this thesis was to explore potentially inappropriate prescribing (PIP) using a mixed methods approach.


Both quantitative and qualitative methodology was used across the three studies contained in this thesis. The first study comprised a systematic review of the tools used to assess PIP in older adults (aged ³65 years) who were receiving polypharmacy and aimed to identify the most appropriate tool for use in research based on a set of criteria deemed to be the key attributes that a tool to assess PIP should possess. The second study was quantitative in nature, using a unique linkage between the Enhanced Prescribing Database (EPD) and the Northern Ireland Longitudinal Study (NILS) to establish the prevalence of polypharmacy (dispensing of 4 or more medicines) and PIP in older adults living in Northern Ireland. In addition, this study determined the predictors for polypharmacy and PIP in both community-dwelling and care home residents and subsequently determined the relationship between polypharmacy, PIP and mortality in the two populations. Finally, a qualitative study, using a topic guide based on the Theoretical Domains Framework (TDF), was undertaken with pharmacists based in GP practices. Semi-structured interviews were conducted with practice-based pharmacists (PBPs) to explore the barriers and facilitators towards managing appropriate polypharmacy in older adults in primary care.


Based on the findings from the systematic review, the Screening Tool Of People’s Prescriptions (STOPP)/ Screening Tool to Alert Right Treatment (START) criteria were determined to be the most appropriate tool to measure PIP in older adults who are receiving polypharmacy. Subsequently, in the second study in this thesis, a subset of the STOPP criteria were used to determine the prevalence of PIP in older adults, the factors associated with PIP and the relationship with mortality. This study revealed that both polypharmacy and PIP was highly prevalent among community-dwelling and care home residents, with the prevalence in the latter significantly higher even after adjustments for health. The majority of predictors for pharmacy and PIP were health-related factors with some residual associations remaining for socio-demographic factors e.g. female gender. Examples of PIP relating to the gastrointestinal (GI), central nervous system (CNS) and indication of medication categories were the most commonly encountered in both community-dwelling and care home residents. In community-dwelling population there was a modest association observed between polypharmacy, PIP and mortality, whereas in the care home population this relationship was not as clear. The qualitative study revealed that all TDF domains except ‘Emotion’ and ‘Nature of behaviours’, were either a barrier, facilitator or both, in managing appropriate polypharmacy in older adults. Pharmacists acknowledged their good professional relationships with GPs acted as a facilitator to managing appropriate polypharmacy, in addition to their clinical knowledge.

Discussion and conclusion:

The work contained in this thesis has added to the growing body of evidence on the use of screening tools to identify and assess PIP. Application of the screening tool highlighted the high prevalence of polypharmacy and PIP among older adults (aged 65 years or older). A particular concern was the high levels of both polypharmacy and PIP in care homes suggesting that there could be a prescribing culture within care homes in NI. Although pharmacists working in GP practices is a relatively new role in NI, they could contribute to a strategy to ensure polypharmacy is prescribed appropriately.
Date of AwardDec 2020
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SponsorsNorthern Ireland Department for the Economy
SupervisorCarmel Hughes (Supervisor) & Dermot O'Reilly (Supervisor)


  • polypharmacy
  • potentially inappropriate prescribing
  • older people
  • practice-based pharmacists
  • screening tools for potentially inappropriate prescribing
  • care homes
  • primary care
  • multiple medicines
  • multimorbidity

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