Exploring the association between stroke and acute myocardial infarction and statins adherence following a medicines co-payment increase

https://doi.org/10.1016/j.sapharm.2021.01.011Get rights and content

Abstract

Objectives

Patient contributions (co-payments) for one months' supply of a publicly-subsidised medicine in Australia were increased by 21% in January 2005 (US$2.73-$3.31 for social security recipients and $17.05-$20.58 for others). This study investigates the relationship between patients’ use of statin medication and hospitalisation for acute coronary syndrome and stroke, following this large increase in co-payments.

Methods

We designed a retrospective cohort study of all patients in Western Australia who were dispensed statin medication between 2004 and 05. Data for the cohort was obtained from State and Federal linked databases. We divided the cohort into those who discontinued, reduced or continued statin therapy in the first six months after the co-payment increase. The primary outcome was two-year hospitalisation for acute coronary syndrome or stroke-related event. Analysis was conducted using Fine and Gray competing risk methods, with death as the competing risk.

Results

There were 207,066 patients using statins prior to the co-payment increase. Following the increase, 12.5% of patients reduced their use of statin medication, 3.3% of patients discontinued therapy, and 84.2% continued therapy. There were 4343 acute coronary syndrome and stroke-related hospitalisations in the two-year follow-up period. Multivariate analysis demonstrated that discontinuing statins increased the risk of hospitalisation for acute coronary syndrome or stroke-related events by 18% (95%CI = 0.1%–40%) compared to continuing therapy. Subgroup analysis showed that men aged <70 years were at increased risk of 54–63% after discontinuing statins compared to those continuing, but that women and older men were not.

Conclusion

Discontinuing statin medication after a large increase patient cost contribution was associated with higher rates of acute coronary syndrome and stroke-related hospitalisation in men under 70 years. The findings highlight the importance of continued adherence to prescribed statin medication, and that discontinuing therapy for non-clinical reasons (such as cost) can possibly have negative consequences particularly for younger men.

Introduction

Affordability of medication is an issue faced worldwide by individuals, families and governments. Out-of-pocket spending on medical services can create barriers to healthcare access and utilisation, including the use of medications.1 In Australia, the Federal Government subsidizes the cost of a wide range of prescription medicines through the Pharmaceutical Benefits Scheme (PBS). Patients make a contribution (co-payment) toward the cost of each dispensed medicine and the remaining cost is paid by the Federal government through the PBS. Co-payments are lower for social security beneficiaries than the general community. Social Security beneficiaries in Australia are also known as concessional beneficiaries. Co-payments are increased each January at a rate equivalent to the consumer price index unit (CPIU) of approximately 3%, however in 2005 copayments were increased by 21% (from AU$3.80-$4.60 (US$2.73-$3.31) for social security beneficiaries and from AU$23.70-$28.60 (US$17.05-$20.58) for general beneficiaries)2,3; the second largest copayment increase in the history of the PBS.

Previous research has demonstrated that rising prescription costs may be followed by a reduction in medication adherence for some people, even for essential medications, and this can result in poorer health outcomes.4, 5, 6, 7, 8, 9 International research has also demonstrated that the reduction in medication adherence due to cost impacts on health service utilisation through increased hospitalisation and emergency department visits.10, 11, 12, 13, 14, 15 Dispensing of statins (HMGCoA reductase inhibitors) – indicated for the primary and secondary prevention of cardiovascular disease (CVD) including coronary heart disease (CHD) and stroke -16,17 was temporarily reduced following the 2005 consumer co-payment increase in Australia.8,9 This led to an immediate 5% reduction in statin dispensings after the co-payment increase. However, the monthly increases in quantity for statin medication remained unchanged demonstrating an immediate but not an ongoing impact of statin utilisation.8

In 2014–15, across Australia there were 1.1 million hospitalisations associated with CVD representing 11% of all hospitalisations nationally.18 However, the risk of hospitalisation due to a cardiovascular event is different for males and females, and across age groups.18

There is potential for a disruption in statin use, as a result of copayment increases making medicines less affordable, to adversely affect health, such as acute coronary syndrome (ACS) and stroke, which could result in additional hospitalisation.

The purpose of this study was to investigate the relationship between consumers who discontinued, reduced adherence or continued statin medications after the January 2005 PBS co-payment increase and ACS or stroke-related hospitalisations using whole-population linked data.

Section snippets

Data sources and ethical considerations

Individual-level data were obtained from both State and Federal databases. Data from the PBS (2002–2010) were linked to the Western Australia (WA) Hospital Morbidity Data Collection (HMDC) (2000–2010) and Mortality Register (2000–2010) by the WA Data Linkage Branch and the Australian Institute of Health and Welfare.19 The PBS dataset captures information about all claims for subsidised medicines dispensed at PBS-approved pharmacies and hospitals. Approval for this study was obtained from the

Results

Characteristics of the study cohort by statin group are shown in Table 1. Overall, there were 207,066 individuals identified as a current statin user at the end of December 2004. Reduction in adherence after the January 2005 co-payment increase was observed in 25,838 (12.5%) and cessation of statin therapy was observed in 6753 (3.3%). The three groups had significant differences in characteristics except for sex and taking diabetic medications in 2004. Compared to the continued group, patients

Discussion

This study investigated the association between statin use following a large co-payment increase in subsidised medicines in Australia and the risk of subsequent hospitalisation for ACS or stroke.

After accounting for the competing risk of death, and controlling for other factors, we showed that patients who discontinued their statin therapy following the co-payment increase had an 18% higher two-year risk of ACS or stroke-related hospitalisations compared with those who continued their therapy.

Conclusion

We found that discontinuing statins was associated with an increased two-year risk of ACS or stroke hospitalisation following a 21% increase in consumer co-payment. Men aged less than 70 years who discontinued their statin therapy had higher risk of ACS or stroke-related hospitalisation. The association was not found in men of other ages and women. This study will help to inform future policy makers on the potential implications of introducing a larger than usual medication co-payment increase.

Authors Statement

Karla L Seaman: Conceptualization, Methodology, Writing – original draft, Formal analysis, Data curation. Max K Bulsara: Writing – review & editing, Supervision, Formal analysis. Frank M Sanfilippo: Writing – review & editing, Supervision, Methodology. Anna Kemp-Casey: Writing – review & editing, Supervision, Methodology. Elizabeth E Roughead: Writing – review & editing, Supervision, Methodology. David B Preen: Writing – review & editing, Supervision, Methodology. Caroline Bulsara, Writing –

Declaration of competing interest

The author reports no conflicts of interest in this work.

Acknowledgments

This study was funded by the National Health and Medical Research Council of Australia (project grant 456408). The authors thank the Australian Department of Health for providing the cross-jurisdictional linked data used in the study. We also thank staff at the WA Data Linkage Branch, and data custodians of the WA Department of Health Inpatient Data Collections and Registrar General for access to and provision of the linked state data.

Abbreviations

SD
standard deviation
CCI
Charlson comorbidity index
CHD
coronary heart disease
CARP
coronary artery revascularisation procedures
ACS
acute coronary syndrome
MPR
medication possession ratio
IQR
interquartile range
CI
confidence interval
sHR
subdistribution hazard ratio
PBS
Pharmaceutical Benefits Scheme
Statins
HMGCoA reductase inhibitors
CVD
cardiovascular disease
WA
Western Australia
HMDC
Hospital Morbidity Data Collection
ATC
Anatomical Therapeutic Chemical
ICD-10-AM
International Statistical Classification of Diseases

References (37)

  • A. Kemp et al.

    Evaluating pharmaceutical policy impact using interrupted time series analysis: an Australia case study

    Int J Public Health Res

    (2011)
  • A. Hynd et al.

    The impact of co-payment increases on dispensings of government-subsidised medicines in Australia

    Pharmacoepidemiol Drug Saf

    (2008)
  • D.P. Goldman et al.

    Prescription drug cost sharing: associations with medication and medical utilization and spending and health

    J Am Med Assoc

    (2007)
  • R. Tamblyn et al.

    Adverse events associated with prescription drug cost-sharing among poor and elderly persons

    J Am Med Assoc

    (2001)
  • M.C. Sokol et al.

    Impact of medication adherence on hospitalization risk and healthcare cost

    Med Care

    (2005)
  • S.B. Soumerai et al.

    Effects of Medicaid drug-payment limits on admission to hospitals and nursing homes

    N Engl J Med

    (1991)
  • N.K. Choudhry et al.

    Full coverage for preventive medications after myocardial infarction

    N Engl J Med

    (2011)
  • T.B. Gibson et al.

    Impact of statin copayments on adherence and medical care utilization and expenditures

    Am J Manag Care

    (2006)
    • View full text
    Crown Copyright © 2021 Published by Elsevier Inc. All rights reserved.