A whole of population retrospective observational study on the rates of polypharmacy in New Zealand 2014 to 2018 Polypharmacy in New Zealand: What is the current status?

Abstract

Background and Aims Polypharmacy (≥5 medicines) and hyperpolypharmacy (≥10 medicines) can significantly impact people's health. The literature surrounding polypharmacy focuses on the elderly, particularly rest home populations, with few studies looking into younger age bands. Moreover, there have been no recent studies looking into the rates of polypharmacy in New Zealand. This study aimed to determine whether polypharmacy rates have increased over time in the New Zealand population. Specifically investigating polypharmacy rates across age and ethnicity, and identifying which medicines are most commonly prescribed in people with polypharmacy. Methods A nationwide retrospective observational study was carried out between 2014 and 2018 on 4 697 274 New Zealanders (96% of the population) by linking dispensing data from the Pharmaceutical Collection to patient enrolment data using a National Health Identifier (NHI) to identify the rate of long‐term medicine prescribing in New Zealand. Results Our study found the rate of polypharmacy to be 9.93% and hyperpolypharmacy to be 1.92% nationwide in 2018, a percentage increase of 4.1% and 7.11% from 2014, respectively. During the same period, we observed the greatest percentage increase (30.37%) in the rate of polypharmacy in the 20 to 29 age band while the rates decreased in older populations. Variation was also noted between ethnicities. Medicines contributing to polypharmacy differed by age group. Conclusion Current methods for minimizing polypharmacy and optimizing medicines use are narrowly focused on the elderly. Despite an increase in education and awareness raising campaigns, rates continue to rise in New Zealand's population.

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“…However, little information exists in large-scale studies worldwide, with the adult population. In this study, a prevalence of polypharmacy of 10.5% was found, a value similar to studies from Poland and New Zealand, which recorded 11.7% and 9.9% of polymedicated individuals, respectively [35,36].…”

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“…We found a successful reduction in polypharmacy among the “75 years and above” subgroups, with a more than 16% reduction in PRR (long-term). A similar study in New Zealand reported a 1–2% reduction in polypharmacy prevalence in older adults between 2014 and 2018 [ 28 ]. The female subgroup showed an approximately 5% greater reduction in PRR (long-term) than the male subgroup.…”

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“… 72 In Australasia, nationwide studies have also observed increases in polypharmacy prevalence. 48 , 78 , 79 Between 2005 and 2013, the proportion of New Zealanders aged ⩾65 years experiencing polypharmacy increased from 23.4% to 29.5% ( p < 0.001), 78 with similar increases in Australia between 2006 and 2014 (33.2–39.8%) among those aged ⩾70 years. 48 However, polypharmacy prevalence among Australians declined over the following 3 years to 36.2% by 2017, 48 with similar patterns of declining rates between 2014 and 2018 among older age groups (⩾60) in New Zealand.…”

“… 48 However, polypharmacy prevalence among Australians declined over the following 3 years to 36.2% by 2017, 48 with similar patterns of declining rates between 2014 and 2018 among older age groups (⩾60) in New Zealand. 79 While this suggests we may be seeing translational outcomes for the efforts made to reduce unnecessary polypharmacy among older adults, during the same time frame (2014–2018) the prevalence of New Zealanders aged 20–29 taking ⩾5 medicines increased by 30.4%. 79 This highlights the potential importance of broadening research to investigate polypharmacy among all adult age groups.…”

“… 79 While this suggests we may be seeing translational outcomes for the efforts made to reduce unnecessary polypharmacy among older adults, during the same time frame (2014–2018) the prevalence of New Zealanders aged 20–29 taking ⩾5 medicines increased by 30.4%. 79 This highlights the potential importance of broadening research to investigate polypharmacy among all adult age groups.…”