Potentially inappropriate prescribing and cost outcomes for older people:
a population prevalence study
Marie Bradley*, Tom Fahey**, Caitriona Cahir **, Kathleen Bennett***, Dermot O’Reilly****,
Carmel M. Hughes*
*School of Pharmacy, Queen’s University Belfast
* ** HRB Centre for Primary Care Research, Department of General Practice, Royal College of Surgeons, Dublin
***Department of Pharmacology and Therapeutics, Trinity Centre for Health Sciences, Dublin
****Centre for Public Health, Queen’s University Belfast,
Introduction
Older people are particularly vulnerable to potentially inappropriate prescribing (PIP)1 because of multiple drug regimens, co-morbid conditions and
age-associated pharmacokinetic and pharmacodynamic changes. Medicines in older people are considered appropriate when they have a clear
evidence-based indication, are well tolerated in the majority and are cost-effective. In contrast, medicines that are potentially inappropriate and have
no clear evidence-based indication, carry a substantially higher risk of adverse side effects compared with use in younger people or are not cost
effective .1 The term “potentially” is used as often, there is little evidence to support the inclusion of certain agents in lists of so-called “bad drugs” and
their use, in specific patients, may be appropriate in some cases. Optimisation of prescribing in older populations is a priority due to the significant
clinical and economic costs of drug-related illness.2
This study aimed to estimate the prevalence and cost of PIP, in an older
population, in Northern Ireland (NI), using European based explicit
prescribing criteria,3 and to investigate the association between PIP,
polypharmacy, gender and age.
Methods
A retrospective cross-sectional study, using primary care
prescribing/dispensing data, from the NI Enhanced Prescribing
Database (EPD), was carried out. EPD comprises a central database of
all prescribed and dispensed drugs, for approximately 1.9 million
patients, registered with general practitioners (GPs) in NI. The study
population comprised all those aged ≥ 70 years (n= 166,108), in the
EPD database, from July 2009-June 2010. Data on all
prescribed/dispensed medications for identified patients, in the given
time period, were extracted from EPD. Twenty eight European based
PIP indicators [Screening Tool of Older Persons Potentially
Inappropriate Prescriptions (STOPP) criteria]3 were applied to the
extracted EPD data. The overall prevalence of PIP and the prevalence
per individual STOPP criteria, were calculated as a proportion of the
total study population. The association between any (vs no) PIP and
polypharmacy (defined as use of 4 or more repeat medications, from
different drug groups) and (categorised as 0-3 vs 4,5......,10+ repeat
drug groups), age, residential status and gender (previously seen as
significant4) was assessed using logistic regression. The maximum
gross ingredient cost and total expenditure analysis is ongoing and
only the prescribing analysis has been presented below.
Results
The overall prevalence of PIP in the study population, in 2009/2010,
was 34% (53,423 patients had at least one PIP). Almost one quarter of
the population, (39,792 patients) were prescribed one potentially
inappropriate medication, 12,014 (7.2%) were prescribed two and
4,617 (2.8%) were prescribed three or more. The most common
examples of PIP identified were the prescribing of proton pump
inhibitors at maximum therapeutic dose for >8 weeks, NSAIDS for
longer than three months, long-term long-acting benzodiazepines and
prolonged use (> 1 week) of first generation anti-histamines (Table 1).
The main predictor of PIP was polypharmacy. The odds of PIP
increased with the number of repeat drug group as shown in Figure 1.
The odds ratio (95% CI) for PIP in those in receipt of 10+ different
medications vs 0-3 medications was 13.86 (13.33-14.40).
Table 1: Top five examples of PIP according to the STOPP criteria
Criteria description
Prevalence (n)
%
PPI for peptic ulcer disease at
maximum therapeutic
dosage for > 8 weeks
17,931
10.79
Long term NSAID use (>3
months)
Long term (>1 month) long
acting benzodiazepines
Prolonged use (> 1 week) of
first generation antihistamines
Long term (>1 month)
neuroleptics
14,545
8.76
10,147
6.10
6004
3.61
5331
3.21
Figure 1. The
association
between
polypharmacy
and PIP
Discussion
Odds Ratio (PIP)
Aim
Number of repeat drug groups vs none
This study has identified a high prevalence of PIP in NI, findings which
are comparable to those in the Republic of Ireland.4 Improving
prescribing in older people remains a major public health issue and
requires close attention by health care professionals. It may have
important implications for primary care and health care costs. Further
research is required to determine why such prescribing takes place, the
extent of negative outcomes and strategies to improve the prescribing of
medicines in older people
References
1. O'Mahony, D. & Gallagher, P.F. Inappropriate prescribing in the older population: need for new
criteria. Age and Ageing 2008; 37: 138-141.
2. Hanlon, J.T., Maher, R.L., Lindblad, C.I., et al. Comparison of methods for detecting potential adverse
drug events in frail elderly inpatients and outpatients. AJHP 2001; 58: 1622-1626.
3.Gallagher, P. & O'Mahony, D. STOPP (Screening Tool of Older Persons' potentially inappropriate
prescriptions): application to acutely ill elderly
patients and comparison with Beers' criteria. Age and Ageing 2008; 37: 673-679.
4.Cahir, C., Fahey, T., Teeling, M et al. Potentially inappropriate prescribing and cost outcomes for older
people: a national population study. Br J Clin Pharmacol 2010; 69: 543-552.
Acknowledgemenmts: The authors would like to thank the staff at the Business Services
Organisation in NI and Maciej Domanski from the Centre for Public Health at QUB.