Prescription medicines, over-the-counter medicines and complementary and alternative medicines use: a comparison between baby boomers and older South Australians

Abstract

1. Introduction

In Australia, the proportion of older people (65 years and over) is projected to increase from 13% (2.6 million people) in 2004 to 26% (6 to 6.3 million persons) by 2051 [1],[2]. The Australian Department of Health and Ageing generally defines the aged as 65 years or more [3]. More specifically, baby boomers have been defined as a person born between 1946 and 1965. There were 4.2 million people born in Australia between these years [4] (excluding baby boomers born overseas). This population group has significantly altered the structure of the population distribution in the second half of the 20^th century. According to the Australian Bureau of Statistics (ABS) in 2003, 27% of the population in the state of South Australia were projected to be baby boomers in 2011 [3] with 23.7% of the population of Australia baby boomers by 2014 [5]. As this group comprises a significant proportion of the population, there is the need to understand, review and optimise the health and social outcomes and, in particular, the use of medications.

A review of the literature indicates that the use of prescription medicines among older people is high, with prevalence rates ranging from 70% to 90% [6]–[11]. The rate of use is increasing, as is the mean number of prescription medicines being taken. In terms of OTC medicines, there are only limited studies and the results are impacted by using different definitions and medicines switching from prescription to OTC. The prevalence of the use of the OTC medicines among adults aged more than 65 years ranged from 31% to 96% between 1981 and 2008 in the United States of America [12]–[16]. In Australia, the prevalence of the use of OTC medicines in older people was 12.8% (1992–1993), 16.6% (1994–1995), 10.0% (2000–2001), and 17.0% (2003–2004) [17], with the overall use lower compared to the United States. In addition, it has been shown that up to two thirds of Australians use CAM [18]. For those Australians aged 65 and older, the prevalence of use was 8.6% in 1992–1993, 14.4% in 1994–1995, 9.0% in 2000–2001, and 24.2% in 2003–2004 [17]. The sale of CAM in Australia was estimated to be worth A$1.2 billion per year in 2008 [19] and in 2011, the Australian Department of Health and Ageing estimated the market growth of complementary medicines to be between 3% and 12% [19]. While CAM use is lower in older populations, the overall trend is increasing [19].

One issue related to any medicine use is polypharmacy. Polypharmacy has, however, been compromised by the use of inconsistent definitions. Polypharmacy refers to the concurrent use of medications. It is often described as taking two or more medicines concurrently over a period of time [11],[20]. The definitions of polypharmacy vary from country to country and there is still no consensus definition. In Australia, polypharmacy is usually defined as five or more drugs including prescribed, OTC medicines, and CAM [21], however, OTC medicines and CAM have not always been included in the definition and study of polypharmacy. In this study, polypharmacy refers to taking five or more medications [21] and for the purposes of this study, major polypharmacy refers to taking ten or more medications. Both definitions include prescription medicines, OTC medicines and CAM.

Details on the combination of the medicines, including prescription medicines, OTC medicines and CAM used by baby boomers and older people is still not fully understood [22]. In addition, little is known about generational differences in medicine use, particularly with regard to CAM and OTC. An assessment of the use of medicines for baby boomers and older people is important due to the increased life expectancy rates, and thus potentially longer periods of medication use, potential medication interactions and changing medication use over time.

This study aimed to examine patterns of use of medicines including prescription medicines, OTC medicines and CAM between older generations, specifically baby boomers and older people, and compare the differences between these two groups. A further investigation of the links between sociodemographic factors and medicines use are also performed. Understanding which medications are used and the differences in medicine usage among these older generations will help inform research and health policy to better meet the health care needs of the future ageing population.

2. Methods

This study used data from the South Australian Health Omnibus Survey (HOS), which was a representative population face-to-face survey conducted in SA annually or biannually between 1991 and 2017. HOS was a “user-pay” survey in which multiple users collected population health data. The operation of this survey was overseen by Population Research and Outcome Studies (PROS), University of Adelaide in conjunction with Harrison Health Research. Harrison Health Research was an accredited organization of Interviewer Quality Control Australia (IQCA). The methodology has been reported previously but is briefly described below [23].

3. Results

In HOS 1, a total of 1,818 people were classified as baby boomers (born between 1946 and 1965) and older people (born before 1946). However, it has been shown that the social and economic characteristics differ between younger and older baby boomers [26]. Thus, for the purposes of this study the baby boomer cohort was divided into a younger (1956–1965) and older (1946–1955) group [27]. There was n = 567 young baby boomers, n = 494 old baby boomers and n = 757 older people. In HOS 2 a total of 1,648 baby boomers and older people were interviewed. There was n = 538 young baby boomers, n = 463 baby boomers and n = 647 older people.

4. Discussion

This study demonstrates that the use of OTC and CAM occurs with prescription medication use and that polypharmacy, including all of these medications, occurs in over 40% of older people. The prevalence estimates for prescription medicines use for older people (approximately 85%) compares to other surveys with ranges between 87% and 90% commonly reported [10],[12],[28]–[32], although lower estimates have been reported from USA (81%) [6]. A comparable Australian study conducted in 2009 and 2010 [28] indicated 87.1% of older people (65 years and over) used prescription medicines, which is in line with our estimates.

Previous studies [33]–[34] have shown conflicting results regarding whether OTC medicine use increases with age, but in this study, the use of OTC medicines clearly increased with age, with estimates of OTC medicines use being 11.7%, 17.7% and 32.8% for young baby boomers, old baby boomers and older people respectively in HOS 2. These prevalence estimates were lower when compared to surveys conducted in USA [6],[13],[33]–[34] with prevalence estimates ranging from 42% to 90%. The discrepancies can be explained by differences in the definition of OTC medicines and differences in subsidised accessibility to prescription medicines. Alternatively, the reported use of OTC medicines for older people (65+ years) in this study (32.8% HOS 2) was higher compared to a previous Australian study, the Australian Longitudinal Study of Ageing (ALSA) [17] which reported a prevalence of 17.7% in 2003–2004. This difference in estimates could potentially be a real increase although ALSA did not classify some medicines, (for example salbutamol inhalers) as OTC medicines, while in HOS 2 salbutamol inhalers were classified as OTC medicines. This again highlights the difference in use of standard definitions in this research area, and the need for a consistent approach.

Conflicting results were also seen regarding the use of CAM, with the use decreasing with age in HOS 1 but increasing with age in HOS 2. The use of CAM increased in older people between HOS 1 (39.2%) and in HOS 2 (59.4%) but decreased use was found in young baby boomers from 58.8% in HOS 1 to 47.5% in HOS 2. These findings raise the question whether CAM use did chang over time in these age groups and a more recent study assessing the use of CAM in baby boomers and older people is required to add clarification to these results. This is important, as the increased use of CAM in older people could potentially increase medicines interactions and adverse reactions. A national population-based survey of Australian people aged over 50 years, conducted in May-June 2005, indicated the prevalence of the use of CAM was 57.8% [28] and another specific study produced estimates of 60.8% for CAM use in SA older people [3]. Again, the prevalence of CAM was slightly higher compared to HOS 1 and HOS 2 and this may be due to the type of CAM included in the national survey with, for example, acupuncture also included in their definition of CAM. ALSA reported the prevalence of the CAM use for older people to be 24.4%. This prevalence was lower than the HOS studies possibly due to the questions being asked in ALSA regarding all medicines used in the past two weeks, instead of the past year as asked in HOS.

The use of CAM in Australia is influenced by media reports. In 2007, Arthritis Australia indicated that fish oil had shown evidence for the relief of rheumatoid arthritis pain [35]. In 2008, the National Heart Foundation released a statement recommending fish oil capsules or liquid to lower the risk of coronary heart disease [36]. Whether these announcements have increased the use of fish oil in the Australian population has yet to be formally determined. However, a study has shown that the Australian Broadcasting Corporation's science journalism program Catalyst program has changed statin use in Australia. The program, which aired in 2013, resulted in a 28.8% decrease in statin continuation [37] in the first week. The results of this study may have been influenced by the Arthritis Australia and National Heart Foundation announcements (as the timeframe of the data collection overlapped with the media reports) and could have association with the use of CAM. The inappropriate use of CAM could significantly impact on the health outcomes of older people and their use in the ageing population is significant [38]–[39].

Moreover, many people are unlikely to disclose their use of CAM to their conventional medical practitioner [40]–[43], with a study showing that as many as 70% of people did not disclose their use of CAM [44]. This contributes to difficulties for health care teams monitoring patients' health outcomes due to the interaction between medicines and natural products and adverse reactions from CAM. This is especially true for older people whose hepatic clearance is deteriorating, which could result in a toxicity of CAM in the body. Nevertheless, CAM use has been shown to be associated with higher health status in ageing populations [45] and the users have been shown to be satisfied with CAM interventions [45].

The presence of marketing forces [46], accessibility to information, existing chronic conditions (i.e. pain, diabetes, cardiovascular disease) and the dissatisfaction of conventional medicine have all been proposed as explanations for the increasing popularity of CAM use [47]. Baby boomers with their higher educational background compared to older people may seek new approaches to address their health needs and expectation. A growing self-empowerment of their own medicines management of their chronic conditions could possibly increase the use of CAM in this generation.

Baby boomer rates of chronic disease are expected to increase exponentially. In all likelihood, baby boomers could further increase their CAM use as their chronic disease profile increases. If this is the case the polypharmacy will also increase. Other important considerations could be the potential for additional adverse reactions associated with medicines use, medicines errors, drug interactions, and less than optimal compliance with medicines regimes, which could all result in additional hospitalisation and increased health expenses.

5. Conclusion

This research has provided additional information and insight into the use of medicines and health outcomes and adds depth to existing knowledge in this domain. Monitoring of medicine-related problems, including the adverse reactions associated with some CAM, long-term effects, ethical implications and overall inappropriate use of medicines is recommended due to the high prevalence and association with polypharmacy. Guidelines need to be promoted highlighting the need for GPs to routinely discuss the risk and benefits of specific CAM approaches with their patients, to promote the safe use of medicines and effective treatment for chronic conditions. Additional education of the public regarding appropriate medicines use is warranted.

The cost implications associated with the high prevalence rates are substantial and requires an overhaul of the Australia health care system in terms of access to medicines use, prescription use, and GP management of medicines to meet the need of older Australians in the near future. A model utilising professions uniquely placed to identify the drug interactions and adverse effects in light of an increased use of prescription medicines and OTC medicines is important to ensure that quality of life is maintained where possible, and better health outcomes are achieved.

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