1 INTRODUCTION

Health care access is effectively defined as the degree to which individuals or communities are able to utilise appropriate health care services that meet their needs. The Behavioural Model of Health Services Use, initially introduced by Andersen in 1968, provides a foundational framework in this field. It identifies three core elements that influence health care utilisation: predisposing characteristics such as social class and education; enabling resources, which include factors like health care costs and insurance coverage; and perceived and clinical needs [1, 2]. This model distinguishes between potential access, which refers to the availability of resources facilitating health care use, and realised access, or the actual employment of health care services, a distinction that has guided numerous studies in understanding health care behaviours and needs [3, 4].

Expanding on Andersen's conceptualisation, McKinlay [5] examined the influence of sociodemographic, socio-psychological, and sociocultural factors alongside economic, geographic, and organisational elements in health care access and utilisation, setting a theoretical basis for later models. Penchansky and Thomas [6] further refined the concept of health care access by describing the alignment between patients and the health care system. Their model, building on Andersen's work, emphasises five dimensions of access: availability, accessibility, accommodation, affordability, and acceptability. These dimensions address various aspects of the patient-health care system interaction, underscoring the importance of ensuring equitable health care service distribution.

The Inverse Care Law, first articulated by Tudor Hart [7] in 1971, posits a paradoxical relationship between the availability of good medical or health care services and the actual need for them within the population. According to this principle, those who need health care services the most, typically individuals from lower socioeconomic backgrounds or residing in underprivileged areas, are often the ones with the least access to high-quality health care. Conversely, those with the slightest necessity for medical services, often individuals from higher socioeconomic groups with better overall health, have the most access to superior health care resources. This concept highlights a fundamental inequity within health care systems, where resources are not always allocated according to need but rather influenced by factors such as income, education, and geographical location. The Inverse Care Law concept underscores the challenges in achieving equitable health care, emphasising the need for targeted policies and interventions that specifically address the disparities in health care access and quality experienced by the most vulnerable segments of the population.

Australia's Medicare system is a foundational pillar of the country's health care infrastructure, offering a universal health scheme to its residents. Established in 1984, Medicare ensures that all Australians have access to a wide range of health and hospital services at little or no cost. It is funded through the country's tax system, which includes a Medicare levy based on individual income levels, to ensure the sustainability and accessibility of health care services [8, 9].

Medicare covers various aspects of health care, including treatment by doctors, specialists, and other health care professionals, hospital care, and, in some cases, prescription medicines and allied health services. Notably, Medicare is designed to provide coverage for both public and private patients in public hospitals, allowing individuals the freedom to choose their preferred health care providers within the public system [9].

One of Medicare's critical features is its role in complementing, rather than replacing, private health insurance. While Medicare offers broad coverage, private health insurance provides additional benefits, such as access to private hospitals, shorter waiting times for elective surgeries, and services that Medicare does not cover, including dental and optical care [10]. This dual system aims to balance the demand between public and private health care services, thereby enhancing the overall efficiency and quality of health care across Australia.

Despite its comprehensive coverage, the Medicare system faces challenges, particularly in funding and resource allocation, to meet the growing health care needs of Australia's population. These challenges underscore ongoing discussions among policymakers, health care providers, and the public on how to adapt and sustain the Medicare system for future generations, ensuring that it continues to provide equitable and quality health care for all Australians [11-13].

The private health care sector, comprising nongovernmental entities such as private hospitals, clinics, and specialists, plays an essential role in complementing the public health care system. Often financed through private health insurance, these services are crucial for alleviating the strain on public hospitals by expanding health care capacity [8, 14]. Most private hospital insurance policies allow patients choose their doctor or specialist and receive treatment as a private patient in a private or public hospital. Around 2 in every 5 hospitalisations in Australia occur in a private hospital [15]. The private sector also adds a competitive element to health care, fostering improvements in service quality, efficiency, and patient satisfaction [16].

Access to private health care in Australia, while significantly contributing to the country's comprehensive health system, which encompasses hospitals and ancillary health options, is marked by several barriers that can limit utilisation for various population groups [8, 17]. These barriers are multifaceted, encompassing economic, geographic, and systemic factors that collectively shape an individual's ability to seek and receive private health care services [8]. The most pronounced barriers to accessing private health care in Australia are economic. The cost of private health insurance premiums has been steadily increasing, often outpacing inflation and wage growth. For many Australians, especially those from lower-income brackets, the rising cost of premiums makes private health insurance unaffordable. Data shows that more than 55% of the Australian population held private health insurance in 2023, representing a total of 14.7 million individuals [18]. Geographic disparities significantly impact access to private health care services in Australia. Private health care facilities, including hospitals and specialist clinics, are predominantly located in urban and affluent areas. This distribution presents a significant challenge for individuals living in rural or remote regions where such facilities are scarce or nonexistent. Consequently, residents in these areas may have to travel long distances for health care, incurring additional costs and inconvenience, which can deter them from seeking private health care services. Furthermore, there is often a perception that private health care is exclusively for the wealthy, detering middle and lower-income individuals from considering it a viable option. This has resulted in individuals in disadvantaged or less affluent areas relying more on public health care services. Lastly, cultural barriers, including language differences and varying health beliefs, further complicate the accessibility landscape for Australia's culturally diverse population.

While Australia's health care system includes both public and private sectors, there is a significant research gap in understanding how these sectors interact and the resulting disparities in access and quality of care. Specifically, there is limited research on how socioeconomic and geographic factors influence the distribution of health care resources between public and private facilities. Additionally, the impact of private health care availability on public health outcomes, particularly in underserved rural and remote areas, remains underexplored. In conclusion, while Australia's private health care system offers significant benefits to those who can access it, addressing the current barriers is crucial to ensuring equitable health care for the entire population. Bridging these gaps requires concerted efforts from the government, the private health sector, and communities to make private health care more accessible and inclusive.

This study aims to investigate whether wealthy populations are predominantly located close to private health care facilities with emergency departments (EDs) by analysing the geospatial distribution of these facilities based on the Index of Relative Socioeconomic Disadvantage (IRSD) and age group.

2 METHODS

The study utilised data from the latest 2021 Census, specifically the Statistical Area Level 1 (SA1) level data on population and IRSD, providing insights into the socioeconomic distribution within the study area. SA1 represents the smallest geographical unit in the census data, encompassing a population range of 200−800 individuals. IRSD is a statistical index used in Australia to rank areas according to their level of economic and social disadvantage. The study also incorporated another data set, the general community profile from the Australian Bureau of Statistics (ABS), which includes information on the population's age distribution within each SA1. Population data were extracted and categorised into two age groups: adults (15–64 years), and seniors (65+ years). These specific age ranges were chosen to examine the accessibility of health care services across age groups and to gain insights into the health care utilisation patterns of adults and seniors. Previous research has highlighted the significance of these age groups in terms of their health care needs and public service utilisation [19].

2.1 Private hospitals with ED

The study focused on private hospitals with a stand-alone ED, where the health care facilities do not share their structure with another public hospital, in the Australian capital cities: Melbourne in Victoria (VIC) (Figure 1); Adelaide in South Australia (SA); Sydney in New South Wales (NSW) (Figure 1); Brisbane in Queensland (QLD) (Figure 1); Hobart in Tasmania (TAS); Perth in Western Australia (WA) (Figure 1). However, Canberra in the Australian Capital Territory (ACT) and Darwin in the Northern Territory (NT) were not included in the study as no stand-alone private hospital with an ED was found.

3 RESULTS

The study integrated the population distribution across age categories (15–64 years, and 65+ years), at distances up to 25 km from each PED.

3.1 Population distribution

The analysis suggests that the spatial positioning of PEDs in the Australian capital cities significantly favours wealthier communities. For people living in immediate proximity (within 1 km) of a PED, the least socioeconomically disadvantaged group (IRSD rank 10) has the highest population (n = 7277). A similar trend prevails for individuals living within 25 km of PED. Moreover, the highest population proportions for both the most disadvantaged (IRSD decile 1) and least disadvantaged (IRSD decile 10) groups appear at distances of 3 km and 14 km. This is evident with population proportions reaching 153,767 for the least disadvantaged and 88,338 for the most disadvantaged group. The least disadvantaged groups remain dominant at virtually all distances. Interestingly, population numbers for both extremes of the IRSD scale seem to decrease after 15 km from PED. This may indicate that fewer individuals reside in these more distant areas regardless of socioeconomic status (SES) (Figure 2).

3.2 Age groups

In the 15–64 age group, a noticeable trend emerges whereby there is a consistent increase in population numbers as we progress from the most disadvantaged to the least disadvantaged group, at virtually all distances from PED (Figure 3). Specifically, for the most proximal group, those living within 1 km, the most socioeconomically disadvantaged group has a population of 1217, while the least disadvantaged group has a population of 5698 (Table 1). The data peaks at 124,780 individuals in the least disadvantaged group (IRSD rank 10) living 3 km away from PED. A similar trend emerges within the 65 and above age category (Figure 4). The numbers generally grow with decreasing levels of socioeconomic disadvantage at all proximities. In the case of those living within 1 km, the most socioeconomically disadvantaged have a population of 654, while the least disadvantaged have a population of 1579 (Table 2). The apex of the population counts in this age bracket is observed at 30,691, corresponding to the least disadvantaged situated 5 km from PED (Figure 4).

Table 1. The number of people aged 15−65 years in each IRSD decile (vertical) at distances 0−26 km (horizontal) from a private hospital with an emergency department.

15–64 age group
	1	2	3	4	5	6	7	8	9	10
0	1217	466	3518	1935	2631	5308	3725	5256	4686	5698
1	7746	8785	17,539	19,035	27,637	32,714	35,259	37,927	43,756	48,000
2	17,253	20,292	23,389	27,547	39,772	50,076	61,364	74,516	79,977	91,750
3	21,584	37,017	42,480	38,951	48,681	63,025	72,376	95,507	116,112	124,780
4	26,309	36,162	41,600	43,997	57,855	69,503	85,834	90,144	114,907	123,537
5	32,463	32,615	41,748	50,113	69,656	81,887	82,382	81,869	105,016	121,073
6	32,072	36,816	49,082	58,393	63,028	64,517	71,399	84,986	85,391	114,359
7	30,901	32,154	51,279	63,156	62,015	59,827	64,961	80,464	78,233	81,411
8	25,762	23,863	39,017	48,396	58,867	62,762	74,031	71,888	76,616	66,898
9	28,764	31,615	45,310	51,869	56,721	58,203	67,550	63,821	78,673	56,122
10	27,623	42,122	41,773	51,079	49,373	57,183	57,701	54,833	64,216	54,094
11	36,107	47,302	45,632	43,690	36,675	40,693	42,268	49,181	47,494	41,309
12	42,550	43,369	40,823	37,744	36,355	37,317	43,952	38,886	39,635	39,874
13	58,437	42,486	37,834	39,149	33,931	38,975	36,244	43,005	38,786	41,357
14	72,162	37,978	36,719	37,661	40,957	39,273	40,298	38,455	38,528	36,585
15	59,826	42,591	33,943	39,754	37,699	34,333	29,620	35,776	34,529	34,093
16	60,782	40,902	36,575	25,915	31,931	34,320	40,753	32,130	42,841	26,061
17	52,981	30,400	28,464	32,888	30,275	33,860	33,178	31,535	36,589	33,447
18	29,721	22,756	28,714	28,527	35,147	33,786	33,915	32,823	31,586	29,396
19	41,598	34,825	39,689	31,920	31,709	29,555	27,091	27,028	26,546	16,902
20	49,154	38,615	24,420	24,590	37,495	26,395	21,910	19,742	21,850	11,890
21	38,212	36,148	22,581	19,134	22,437	24,532	29,919	17,448	15,677	10,394
22	24,698	17,175	20,719	21,602	19,957	16,938	15,831	14,491	13,648	6443
23	11,045	12,747	14,332	21,283	18,000	8937	12,925	9914	4183	2447
24	6926	9408	17,167	20,292	17,552	13,431	7069	9020	5571	3137
25	1530	1825	3229	2968	5432	3308	2612	821	801	1087

• Note: 0 represents 0–1 km (but not including 1 km), and 25 represents 25–26 km (but not including 26 km).
• Abbreviation: IRSD, Index of Relative Socioeconomic Disadvantage.

Table 2. The number of people aged 65 and over in each IRSD decile (vertical) at distances 0 to 26 km (horizontal) from a private hospital with an emergency department.

65+ age group
	1	2	3	4	5	6	7	8	9	10
0	654	587	720	590	495	1259	899	1303	1289	1579
1	2943	2498	3793	4581	5270	6693	8601	7897	10,312	9884
2	6346	5997	6051	6015	9611	11,609	14,514	15,235	18,357	21,222
3	7470	9905	10,222	10,545	11,143	15,374	16,212	21,549	26,842	28,987
4	9712	10,430	10,467	12,412	15,495	16,954	19,588	22,139	25,675	29,411
5	10,417	9628	12,016	14,462	17,967	18,223	19,241	19,989	25,314	30,691
6	10,108	13,638	14,749	14,372	17,231	15,949	18,052	20,333	21,457	28,517
7	8561	10,860	13,357	14,120	15,393	15,348	15,623	18,464	19,133	19,029
8	6696	7940	10,489	12,821	14,785	15,801	17,221	15,876	18,510	16,887
9	9371	7778	11,387	14,004	15,462	13,238	14,608	14,834	17,026	12,415
10	7222	9210	11,074	12,565	13,216	13,381	12,798	11,387	13,271	12,975
11	9410	12,167	10,206	11,240	9596	10,518	10,815	11,372	11,408	9475
12	11,964	11,294	9972	8843	8547	9616	11251	9233	9363	12,227
13	15,037	9335	9307	9773	8126	8663	9068	10,658	10,707	10,806
14	16,176	8506	8897	7983	8437	9458	8713	9149	8208	8449
15	13,373	9492	6651	8353	7340	6960	6609	7951	7629	8178
16	15,961	8891	7565	5395	6801	8467	7743	5858	8431	5682
17	13,446	6804	7807	6716	6327	7061	6241	5891	6375	5995
18	7726	5073	7260	5999	8393	6913	6673	6287	5524	4747
19	9671	8459	8143	6466	7286	6900	5500	5563	5173	3245
20	11,189	8831	5881	5886	7352	5377	3757	4407	3764	1992
21	7792	8584	5695	4304	4581	5125	6283	4024	3288	2399
22	6442	5945	5015	4692	3948	3020	3336	3408	2927	1394
23	3490	4153	4166	5606	3890	2063	2754	1886	602	530
24	3884	2530	4182	4065	3560	2750	1245	1688	1112	611
25	732	672	635	571	1318	841	694	161	117	271

• Note: 0 represents 0–1 km (but not including 1 km), and 25 represents 25–26 km (but not including 26 km).
• Abbreviation: IRSD, Index of Relative Socioeconomic Disadvantage.

4 DISCUSSION

This study aimed to scrutinise the distribution of PEDs within Australian capital cities, focusing primarily on the surrounding area-level SES and employing Geographic Information System for detailed visual comprehension. Health affordability emerges as a central concern globally, influencing individuals' and communities' well-being and quality of life through the prism of medical service costs, insurance coverage, and access to quality care. It underlines the need for all individuals to have a fair opportunity to reach their full health potential, regardless of social, economic, or environmental circumstances [22].

The study further revealed accessibility variations across age groups, with both the adult (15–64 years) and senior (65+ years) cohorts experiencing enhanced access to PEDs amidst decreasing socioeconomic disadvantages. This trend suggests a systemic advantage that might influence overall health outcomes for these demographics. It becomes crucial to factor in these age groups' specific health care needs and utilisation patterns, particularly as older adults often necessitate more immediate health care interventions.

The analysis illuminated a clear pattern: individuals residing in less socioeconomically disadvantaged areas (highest IRSD decile) enjoy closer proximity to PEDs and constitute the highest population counts within a 1−25 km radius. This trend exemplifies the Inverse Care Law's manifestation within the Australian context, suggesting wealthier populations have more accessible emergency health care services. The findings align with the wealth-health gradient proposed by Frijters [23], who assert that wealthier individuals have better health outcomes because they have superior access to health care resources. Previous research also highlighted that health care accessibility is a multifaceted issue shaped by various socio-demographic elements [24]. Yet, it is also noteworthy to observe the decrease in population counts for both extremes of the IRSD scale beyond 15 km from private hospitals. This trend may point to other noneconomic factors influencing hospital distribution, such as private insurance availability, population density and urban-rural divides [25, 26]. Consequently, it suggests that the relationship between private hospital distribution and wealth distribution may be interwoven with other socio-demographic factors, illustrating the multidimensional nature of health care accessibility.

5 CONCLUSION

In conclusion, while Australia's private health care sector is an integral part of the national health system, accessibility to private health care is significantly influenced by geographic location, SES, and health insurance coverage. The IRSD serves as a valuable indicator for understanding the intricate relationship between private health care accessibility and socioeconomic disadvantage. To address these disparities, there is an urgent need for robust health policies that promote a more equitable distribution and integration of private health care facilities across the country. These policies should ensure equal access to health care services regardless of SES or geographical location, particularly in light of the challenges highlighted by the COVID-19 pandemic.

Furthermore, special emphasis must be placed on enhancing health care accessibility in rural and remote areas, where private health care services are markedly underrepresented. This could involve strategic planning to establish new health care facilities, revise transportation and referral systems, and provide targeted subsidies for low-income populations. By prioritising these efforts, significant strides can be made in reducing health disparities and fostering a more inclusive health care system that meets the needs of all Australians, regardless of their socioeconomic or geographic circumstances.

AUTHOR CONTRIBUTIONS

Mazen Baazeem, Estie Kruger, and Marc Tennant wrote the main manuscript text. Mazen Baazeem analysed the data and prepared the tables and figures. All authors reviewed the manuscript.

CONFLICT OF INTEREST STATEMENT

The authors declare no conflict of interest.

ETHICS STATEMENT

Exemption from ethics review was obtained from the Human Research Ethics Committee at the University of Western Australia (Approval number—2021/ET000358).

INFORMED CONSENT

Not applicable.