Pharmacoepidemiology and economic evaluation of measures of potentially inappropriate prescribing

Background: Several measures of potentially inappropriate prescribing (PIP) exist, however their validity has been under-researched. The aim of this thesis was to assess measures of PIP in older and middle-aged people in primary care in terms of their applicability and relevance in Ireland, effect on patient outcomes and economic impact.

Methods: This thesis focussed on community-dwelling adults in Ireland, aged ≥65 years (older adults) or 45-64 years (middle-aged adults). Measures of PIP, the Screening Tool for Older Persons’ Prescriptions (STOPP), the Screening Tool to Alter doctors to Right Treatment (START), and PRescribing Optimally in Middle-aged People’s Treatments (PROMPT) criteria, were applied to two national data sources, the General Medical Services (GMS) scheme dispensing database and The Irish Longitudinal Study on Ageing. Economic analysis was also conducted by developing Markov models of PIP.

Results: The prevalence of PIP in older people rose from 1997 to 2012 (32.6%-37.3%), though the odds of having PIP decreased over time after accounting for the increase in medications prescribed. Long-term prescribing of maximal dose proton pump inhibitors grew sharply and was not consistently associated with expected risk factors for gastrointestinal bleeding. PIP was present in 41.6% of middle-aged GMS patients, with prevalent criteria similar to those in older people. For older adults, having ≥2 STOPP criteria was significantly associated with higher rates of emergency department and GP visits, while having ≥2 START omissions was also associated with increased healthcare utilisation, functional decline and reduced quality of life (QoL). In middle-aged people, there was no evidence of a relationship between PROMPT criteria and healthcare utilisation or QoL after controlling for confounders. Of the three PIP criteria evaluated relative to appropriate alternatives in Markov models, long-term benzodiazepine prescribing had the greatest cost and quality-adjusted life year impact, although long-term non-steroidal anti-inflammatory drug use was the most costeffective PIP to target.

Conclusion: This thesis demonstrates that PIP is prevalent and can impact on patient and economic outcomes. Optimising prescribing to reduce PIP may provide benefits for patients and the wider health system.