Enhancing Health Equity in China: The Interplay of Public Health Infrastructure, Service Utilization, and Health Insurance

Abstract

The COVID-19 pandemic exposed significant deficiencies in global health emergency preparedness, highlighting the critical importance of health equity. This study investigates the role of public health infrastructure in promoting health equity, utilizing data from 31 provincial regions in China. The analysis examines the mediating role of medical service utilization (hospitalization and outpatient services) and the moderating effect of health insurance. The findings indicate that public health infrastructure is significantly associated with health equity. Medical service utilization partially mediates this relationship, with health insurance further moderating the positive impact of hospitalization utilization on health equity, though not for outpatient services. Regional analysis reveals heterogeneity, with public health infrastructure exerting a significant effect on health equity in the central–western regions but not in the eastern region. This research underscores the importance of accessible public health infrastructure and comprehensive health insurance in eliminating health disparities, providing valuable insights for policymaking aimed at fostering health equity.

1. Introduction

The sudden outbreak and global spread of the novel coronavirus (COVID-19) pandemic presented immense challenges for public health systems worldwide, highlighting deficiencies in health emergency preparedness systems. This crisis has not only underscored the critical importance of health equity across diverse nations but also prompted a reevaluation of societal priorities [1]. Health equity, as articulated by Whitehead and the World Health Organization, shows that “everyone should have a fair opportunity to attain their full health potential and, more pragmatically, that no one should be disadvantaged from achieving this potential if it can be avoided” [2]. This principle underscores the need for deliberate efforts to eradicate health disparities among different societal groups. Emphasizing health equity serves as a guiding principle for fostering sustainable development that is not only just and prosperous but also resilient in the face of future uncertainties. By ensuring easy access to healthcare and addressing social determinants of health, a country can establish a foundation for sustainable development that promotes equitable well-being and societal resilience.

In practice, promoting health equity needs to eliminate barriers to health inequity, such as equitable access to public health infrastructure, better medical service utilization, and promoting health insurance. Public health infrastructure is widely regarded as one of the essential healthcare resources that affect residents’ health and well-being [3]. Medical service utilization shows the extent to which individuals access and use medical services to address their health needs [4]. It encompasses the patterns, frequency, and intensity of medical service utilization, such as hospitalization utilization and outpatient utilization [5], by individuals within a given timeframe. The increasing utilization of medical services puts pressure on individuals, and the health insurance system is an important mechanism for guaranteeing the use of medical services [6]. Health insurance helps reduce the burden of medical services for the insured by lowering the economic threshold for receiving medical services, thereby improving the health of the insured to a certain extent [7].

Public health infrastructure has received a lot of attention from researchers. Some research shows that public health infrastructure plays a role in promoting health equity [8,9]. On the one hand, a sound public health infrastructure might increase convenience for people, protect their rights to life and health, and promote social stability [10]. On the other hand, the development of public health infrastructure may help eliminate poverty and raise people’s living standards. However, some studies found that the relationship between the availability of public health infrastructure and health equity is not significant [11]. Internationally, similar disparities in public health infrastructure are evident, with low-income countries often lacking the resources to invest in modern healthcare facilities and advanced diagnostic equipment. In China, the development of public health infrastructure has been uneven across regions. For example, while eastern regions have benefited from substantial investment in modern healthcare facilities and advanced diagnostic equipment, rural and western regions often struggle with inadequate medical resources and outdated infrastructure [12]. In the post-epidemic era, governments are required to pay attention to the construction of public health infrastructure, and the social effects of public health infrastructure have also become the focus of academic attention. Investigating the relationship between public health infrastructure and health equity is imperative, as it would enhance the understanding of how the equitable distribution of public health infrastructure may influence health equity.

Medical service utilization is a factor in predicting health equity. An increase in the level of medical service utilization does not mean that people are sicker, but rather that they can afford to go to the doctor [13]. Globally, health insurance systems vary significantly, with different coverage levels and reimbursement policies affecting health equity. For example, in low- and middle-income countries, inadequate health insurance coverage often leads to high out-of-pocket expenses, further exacerbating health inequities [14]. In China, there is a significant urban–rural divide in medical service utilization, with urban residents having higher utilization rates due to better access to healthcare facilities and higher income levels [13]. Better utilization of medical services may have a positive impact on people’s health improvement and, in the long run, contribute to societal health equity [15]. However, medical service utilization may require prerequisite factors, for example, public health infrastructure. The construction of public health infrastructure ensures that individuals have easy access to essential medical services, which might lead to higher utilization rates as people are more likely to seek care when services are readily available.

Existing studies also investigate the impact of health insurance on health equity. Han and Meng [7] found that the type of health insurance does not affect health service utilization by the floating elderly population in China, but participation in different regions will significantly affect the use of health service resources and further impact the health equity for those participating in the same health insurance. Others showed that by improving the health services utilization of insured persons against the risk of medical expenditures, health insurance has a positive effect on the health of citizens and health equity to some extent [16,17]. Considering the conflicting results, more research is needed to unravel the mechanism by which health insurance affects health equity.

China’s vast size and varying levels of economic development across regions provide a unique context for examining health equity. The country has witnessed significant disparities in healthcare access and outcomes between urban and rural areas, as well as among different provinces. Therefore, given the theoretical gaps, this study aims to investigate the mechanism and conditions to improve health equity by assessing the mediating role of medical service utilization and the moderating effect of health insurance, based on statistical data on 31 provincial administrative regions in China from 2011 to 2020. Specifically, we attempt to answer the following research questions: (1) Is public health infrastructure empirically associated with health equity? (2) What are the mediating roles of medical service utilization and the moderating role of health insurance? By investigating the relationships between public health infrastructure, medical service utilization, health insurance, and health equity in China, this research enriches the theoretical research on health equity and facilitates our understanding of how to promote health equity by combining different influencing factors.

Following the introduction, Section 2 reviews the literature and proposes hypotheses. Section 3 presents the research model and variable specifications, followed by the empirical analysis results in Section 4. The discussion and contributions are presented in Section 5.

2. Literature Review and Hypotheses Development

2.1. Health Equity

The COVID-19 pandemic has had profound and lasting impacts on public health systems and health equity globally. Globally, the COVID-19 pandemic has revealed significant disparities in health equity, with countries like the United States and Brazil experiencing severe health disparities due to unequal access to healthcare resources and social determinants of health. In contrast, countries with more equitable healthcare systems, such as Norway and Canada, have demonstrated better health outcomes during the pandemic [18]. In many regions, the pandemic has highlighted the importance of robust public health infrastructure, equitable access to healthcare services, and comprehensive health insurance systems to mitigate the effects of such crises. The pandemic has also underscored the need for a more integrated approach to health equity, emphasizing the importance of addressing social determinants of health, such as income inequality, education, and access to healthcare services [19].

Health equity, where every person has a fair and just opportunity to be as healthy as possible, is increasingly listed as a priority by healthcare organizations and policymakers. It has also received a lot of attention from researchers in recent times [20,21]. The words “health equity” or “health equality” are used interchangeably in research [22], but there is a difference between the two. Health equity demonstrates the ethical and human rights principle that seeks to eliminate health disparities, which are avoidable differences in health or its main influencing factors (such as income, education, medical service utilization, health insurance, and safe environment) that adversely affect vulnerable or excluded groups. Health equality refers to the differences (if any) in health status that are generated because of demographic, geographic, and other given conditions [23]. Health equality is a broad term that includes health equity and signifies more than just difference or variation. Additionally, health equality is easily measured compared with health equity. Specific tools such as the Social Vulnerability Index, Social Determinants of Health in Rural Communities Toolkit, National Equity Atlas, and Neighborhood Atlas are used to measure health equity [24].

Internationally, health equity is a critical issue, with many countries facing challenges in achieving equitable healthcare access and outcomes. For example, in the European Union, significant disparities in health equity have been observed between member states, with Eastern European countries often lagging in healthcare infrastructure and social determinants of health. Similarly, in Africa, the lack of robust public health infrastructure and limited access to healthcare services have led to significant health disparities, particularly in rural areas [25]. Health equity can be regarded as both a process and an outcome. As a process, health equity aims to remove obstacles to the health of everyone, especially those who have been excluded and marginalized. It can also be viewed as the process of reducing and ultimately eliminating disparities in health and health determinants that adversely affect vulnerable or excluded groups [26]. As an outcome, the ultimate goal of health equity is to achieve fair and just opportunities for everyone to achieve good health, or to eliminate health and health-determinant disparities that adversely influence disadvantaged groups. In this research, we view health equity as an outcome and aim to identify the factors that influence disadvantaged groups, providing suggestions to eliminate health disparities.

Achieving health equity requires addressing equity not only in health care but also in the social determinants of health and health care, such as healthcare access and use, education, income, and wealth gaps [27,28]. In China, the pursuit of health equity is particularly challenging due to significant regional disparities in economic development and healthcare resource allocation [29]. China’s provinces have varying levels of economic development, resulting in an uneven distribution of healthcare infrastructure and healthcare resources. For example, the number of healthcare institutions and personnel per capita is significantly higher in the eastern regions compared to the central and western regions. Additionally, the urban–rural divide is pronounced, with urban areas having better-equipped medical facilities and higher physician density. This disparity is further exacerbated by the fact that some provinces, particularly those in the western and central regions, face challenges such as high medical costs, limited insurance coverage, and insufficient public health emergency response capabilities. Existing research has majorly focused on the antecedents of health equity. Lewis, et al. [30] classified the conditions linked to health equity into six main antecedent categories, including (a) environmental, (b) financial and economic, (c) law, political, and policy, (d) societal and structural, (e) research, and (f) digital divide and technology. Boeckmann and Zeeb [31] considered socioeconomic factors like antidiscrimination, gender equity, fairness, and protecting cultural diversity as antecedents of health equity. These studies mainly used qualitative methods to explore the antecedents, ignoring the complex relationships between antecedents and health equity. This research aims to fill the research gaps and provide useful suggestions on improving health equity.

2.2. Proposed Hypotheses

To clarify the role of public health infrastructure in health equity, and based on the existing literature, we attempt to propose some theoretical hypotheses. Figure 1 illustrates the research model.

Public health infrastructure is the foundation of facilities and resources that support the delivery of healthcare services within a community, region, or country. It provides the physical framework and facilities, such as hospitals, clinics, primary care centers, and specialist care facilities, where healthcare services are delivered [32]. Public health infrastructure is closely connected with our lives and health. Feng and Yuan [10] showed that a sound public health infrastructure can facilitate easy access to healthcare for people, protect their rights to life and health, and further contribute to the social stability and economic growth of the society. Baum-Snow and Pavan [33] presented that a region with a high level of public health infrastructure could attract inflows of people seeking medical treatment and high-quality workers.

The public health infrastructure is also closely related to health equity, although this equity may vary depending on the unequal distribution of resources and socio-economic status of the region [12]. A sound public health infrastructure in a region can provide perfect medical conditions and ensure that healthcare services are geographically and financially accessible to all members of society [34]. This accessibility reduces disparities in health outcomes by enabling timely access to preventive care, diagnostics, and treatment [1]. In addition, a well-developed public health infrastructure that includes well-trained healthcare professionals, modern medical equipment, and evidence-based practices, strives to provide high-quality healthcare services across the board [35]. Consistent quality of care ensures that individuals receive appropriate and effective treatments regardless of their background, thus contributing to health equity. In addition, effective public health infrastructure facilitates the implementation of preventive healthcare measures such as vaccinations, screenings, and health education programs, to address health disparities at their root, reduce the burden of preventable diseases among vulnerable or excluded groups, and promote overall health equity. Therefore, we can propose our first hypothesis.

Hypothesis 1:

Public health infrastructure is associated with health equity.

Despite public health infrastructure playing an important role in promoting health equity, public health infrastructure is only one type of factor and cannot replace other factors. Prior studies indicate that medical service utilization, including hospitalization utilization and outpatient utilization, plays an important role in achieving health equity [5]. However, there is little research explaining the mechanisms through which public health infrastructure influences health equity. Medical service utilization, which refers to the extent to which individuals access and use healthcare services when needed [36], logically becomes a link that connects public health infrastructure with health equity.

However, the relationship between public health infrastructure and health equity is not always straightforward. Some studies have found that while public health infrastructure can improve access to healthcare services, it may not necessarily lead to better health outcomes or reduced health disparities [11]. For example, in regions with high levels of public health infrastructure, disparities in health outcomes may persist due to other factors such as socioeconomic status, education, and cultural barriers [37]. These findings suggest that public health infrastructure alone may not be sufficient to achieve health equity and that a more comprehensive approach is needed.

On the one hand, effective utilization of medical services, including hospitalization utilization and outpatient utilization, plays a pivotal role in promoting health equity among diverse populations. Firstly, frequent use of outpatient services facilitates continuous management, monitoring, and support for individuals with chronic health conditions. This ongoing care includes regular check-ups, medication management, and disease management programs, which are crucial in helping individuals effectively manage their conditions and prevent health complications [38]. By providing these services equitably, disparities in health outcomes among populations with chronic illnesses can be significantly reduced. Secondly, hospitals serve as essential facilities for maternal and child health services, encompassing critical areas like labor and delivery, neonatal intensive care, and pediatric care. Ensuring equal access to these services is indispensable for lowering maternal and child mortality rates and improving health equity across all sectors of society. Additionally, hospitals offer advanced diagnostic services such as imaging and laboratory tests, as well as therapeutic interventions like chemotherapy and radiation therapy. These services are essential for accurately diagnosing and treating complex medical conditions, further contributing to enhanced health outcomes and equity.

On the other hand, the availability, accessibility, quality, and organization of public health infrastructure significantly influence individuals’ utilization of medical services, including hospitalization utilization and outpatient utilization [39]. First, the presence of well-developed public health infrastructure, including hospitals, clinics, and healthcare centers, enhances geographic accessibility to medical services [40]. Regions with well-established public health infrastructure tend to exhibit higher rates of medical service utilization due to improved accessibility. In contrast, areas lacking sufficient medical facilities may experience lower utilization rates, particularly in underserved or remote communities. Second, the range and variety of healthcare offered within public health infrastructure influence individuals’ medical service utilization patterns [41]. Comprehensive public health infrastructure that provides a spectrum of services—from preventive care and diagnostics to specialized treatments—facilitates proactive healthcare-seeking behavior. Individuals are more likely to utilize medical services when they have access to a broad range of healthcare options within their vicinity [42]. Conversely, limited availability or specialization of medical services in certain regions may lead to underutilization or delayed access to necessary healthcare interventions. Third, rapid access to hospitalization services during emergencies ensures timely interventions and reduces morbidity and mortality rates. In addition, the availability of specialized medical equipment and skilled healthcare professionals in hospitals enhances the capacity to manage complex medical cases effectively.

Based on the analysis above, well-equipped public health infrastructure plays a pivotal role in shaping individuals’ utilization of medical services, including hospitalization utilization and outpatient utilization, by influencing accessibility, availability, quality, etc. The better utilization of medical services provides individuals with opportunities to mitigate disparities and promote health equity. Accordingly, we can propose our second theoretical hypothesis:

Hypothesis 2a:

Hospitalization utilization mediates the positive relationship between public health infrastructure and health equity.

Hypothesis 2b:

Outpatient utilization mediates the positive relationship between public health infrastructure and health equity.

Despite the importance of medical service utilization being widely recognized, not all individuals are willing to utilize medical services as it may increase their expenses. High medical expenditure has become an obstacle to people’s health. Some studies have found that the relationship between health insurance and health equity is not always straightforward. While health insurance can improve access to healthcare services, it may not necessarily lead to better health outcomes or reduced health disparities [7]. Finkelstein et al. (2012) highlighted that health insurance coverage alone may not be sufficient to address health inequities, as other factors such as the quality of care, provider networks, and socio-economic status also play a crucial role [16]. Recently, policymakers and scholars have increasingly touted health insurance as a prevailing view for the understanding of health equity [43,44].

Health insurance is a type of insurance coverage that pays for medical and surgical expenses incurred by the insured. It functions as a financial safety net, helping individuals or families manage the high costs associated with medical services, such as doctor visits, hospital stays, prescription medications, surgeries, and other medical procedures [45]. Health insurance policies may vary in terms of coverage, cost, and provider networks. Some policies cover only basic medical services, while others offer comprehensive coverage for a broader range of medical service needs.

In China, the health insurance system includes multiple schemes such as the Urban Employee Basic Medical Insurance, Urban Resident Basic Medical Insurance, and New Rural Cooperative Medical Scheme, each with different coverage levels and reimbursement policies [7]. These schemes aim to reduce the financial burden of medical expenses for individuals, but their effectiveness varies across regions. In regions with comprehensive health insurance, the financial burden of individuals will be reduced. This can help improve medical service utilization and narrow the differences in treatment between different medical insurance schemes. It can also enhance the sense of well-being and realize the equalization of basic public health services. Additionally, comprehensive health insurance often covers preventive services such as vaccinations, screenings, and annual check-ups at little to no cost to the insured individual [46]. Increased access to preventive medical services can help detect health issues early, prevent them from becoming more serious and costly to treat later on, and promote people’s health and equity. Therefore, in areas where health insurance coverage is widespread, people would typically expect to see a stronger positive relationship between medical service utilization and health equity, as health insurance helps bridge the gap in access to healthcare services for individuals regardless of their socioeconomic status. Based on the analysis above, this study proposes that:

Hypothesis 3a:

Health insurance moderates the positive relationship between hospitalization utilization and health equity, so this relationship is stronger in the presence of health insurance.

Hypothesis 3b:

Health insurance moderates the positive relationship between outpatient utilization and health equity, so this relationship is stronger in the presence of health insurance.

3. Model and Variable Specification

3.1. Model Design

According to Hypothesis 1, Equation (1) can be constructed to test the effect of public health infrastructure on health equity.

$$Y_{it}={\alpha }_0+{\alpha }_1{X}_{it}+{\alpha }_2{C}_{it}+{\epsilon }_{it}$$

(1)

where i is the province or municipality; t represents the year; $Y_{it}$ represents health equity; $X_{it}$ represents public health infrastructure; $C_{it}$ represents the control variables; ${\alpha }_0$, ${\alpha }_1$, ${\alpha }_2$ are constants; and ${\epsilon }_{it}$ is the random disturbance.

Based on Hypotheses 2a and 2b, Equations (2) and (3) can be constructed to test the mediating role played by medical service utilization between public health infrastructure and health equity.

$$X_{it}={\beta }_0+{\beta }_1{ME}_{it}+{\beta }_2{C}_{it}+{\epsilon }_{it}$$

(2)

$$Y_{it}={\gamma }_0+{\gamma }_1{X}_{it}+{{\gamma }_2{ME}_{it}+\gamma }_3{C}_{it}+{\epsilon }_{it}$$

(3)

where ${ME}_{it}$ represents medical service utilization; ${\beta }_0$, ${\beta }_1$, ${\beta }_2$, ${\gamma }_0$, ${\gamma }_1$, ${\gamma }_2$, ${\gamma }_3$ are constants.

According to Hypotheses 3a and 3b, Equation (4) can be constructed to test the moderating role played by health insurance between medical service utilization and health equity.

$$Y_{it}={\mu }_0+{\mu }_1{ME}_{it}+{{\mu }_2{MO}_{it}+{\mu }_3{ME}_{it}\ast {MO}_{it}+\mu }_4{C}_{it}+{\epsilon }_{it}$$

(4)

where ${MO}_{it}$ represents health insurance; ${\mu }_0$, ${\mu }_1$, ${\mu }_2$, ${\mu }_3$, ${\mu }_4$ are constants.

3.2. Variable Selection

The explained variable is health equity. Following existing research [47,48,49,50], the maternal mortality rate directly reflects the accessibility, quality, and equity of maternal health services, while the difference in the mortality rate of infectious diseases in categories A and B may reveal gaps in the public health system and the vulnerability of specific populations (e.g., poor populations, migrant populations). The World Health Organization uses them as key output indicators of the “social determinants of health” to assess health inequalities within/among countries [51]. Moreover, the United Nations has included the two indicators as core monitoring targets for global health equity. Therefore, it is suggested to combine them to provide a better reflection of the multidimensional connotation of health equity and to more comprehensively capture equity issues across various health domains [52]. By combining the two indicators of maternal mortality rate and the mortality rate of infectious diseases in categories A and B, we adopted the entropy weight method, which objectively describes the data characteristics, to obtain their weights for the combination of the two indicators [53]. We then applied Min–Max standardization to this comprehensive index to represent health equity.

The explanatory variable is public health infrastructure. Following Cao, et al. [54], Li, et al. [55], and Yan, et al. [32], and similar to the explained variables, we constructed a composite index to comprehensively capture public health infrastructure using the entropy weight method, followed by Min–Max standardization. The composite index consists of indicators in three areas: personnel, capital, and facilities. Specifically, it comprises health technicians per 1000 people, occupational (assistant) physicians per 1000 people, registered nurses per 1000 people, the percentage of total health costs in GDP, the number of hospitals per 10,000 people, and the percentage of specialized public health institutions in the number of health institutions.

The mediator variable is medical service utilization, which includes hospitalization utilization and outpatient utilization. According to Diehr, et al. [56], Ma, et al. [57], and Zhou, et al. [58], we reflect hospitalization utilization and outpatient utilization by the annual resident hospitalization rate and the average annual number of resident visits, respectively.

The moderator variable is health insurance. Following Qian, et al. [59], Zhang, et al. [60], and Zhu, et al. [61], we adopt the logarithmic value of per capita basic health insurance fund expenditures to reflect health insurance.

Moreover, following Emerson, et al. [62], Li, et al. [63], Shah [64], and Sun [65], we select the percentage of the population aged 65 and above in the working age population (Elderly dependency), the percentage of illiterate population in the population aged 15 years and above (Illiterate population), and the percentage of population aged 65 years and above (Population aged ≥ 65) as control variables.

3.3. Data Source

Given the data availability and maintaining the harmonization of statistics, this study selects 31 provinces, autonomous regions, and municipalities in China (excluding Hong Kong, Macao, and Taiwan), and empirically analyzes them using the panel data of each province or municipality from 2011 to 2020. The data for three control variables were obtained from the China Statistical Yearbook, and the remaining variables were derived from the China Health Statistics Yearbook. The results of the descriptive statistical analysis of all variables are shown in

Table 1. Descriptive statistics of variables.

Variable	Obs	Mean	SD	Potential Range	Actual Min	Actual Max
Health equity in raw data	310	5.489	5.607	≥0	0.673	49.277
Standardized health equity	310	0.901	0.115	0–1	0	1
Public health infrastructure in raw data	310	1.767	0.376	≥0	1.094	3.149
Standardized health equity	310	0.328	0.183	0–1	0	1
Hospitalization utilization (%)	310	15.137	3.719	0–100	3.200	24.100
Outpatient utilization	310	5.397	1.852	≥0	2.670	11.650
Health insurance	310	7.185	0.448	≥0	6.120	8.750
Elderly dependency (%)	310	14.332	3.811	≥0	6.710	25.48
Illiterate population (%)	310	5.903	6.106	0–100	0.890	41.18
Population aged ≥ 65 (%)	310	0.169	0.193	0–100	0.050	0.810

, where the explanatory and explained variables are pre-standardization data.

To avoid regression bias due to multicollinearity among variables, this study conducts a multicollinearity test, as presented in

Table 2. Test for multicollinearity.

Variable	VIF	1/VIF
Public health infrastructure	1.68	0.596
Hospitalization utilization	1.60	0.624
Outpatient utilization	1.70	0.590
Health insurance	2.31	0.433
Elderly dependency	1.54	0.650
Illiterate population	1.28	0.783
Population aged ≥ 65	1.11	0.901
Mean VIF	1.60

. The VIF (variance inflation factor) for each variable is smaller than 5, which indicates that there is no multicollinearity between these variables.

4. Empirical Results

4.1. Baseline Regression

In this study, Stata 18.0 was used for the regression analysis of the data. We adopted the Hausman test to choose between the random effects model and the fixed effects model. The Hausman test shows that chi2(8) = 43.53 and Prob > chi2 = 0.0000, hence the fixed effects model should be selected for the regression. The results of the baseline regression are demonstrated in

Table 3. Baseline regression results.

	Health Equity
	(1)	(2)	(3)	(4)
Public health infrastructure	0.102 *** (4.772)	0.188 *** (5.492)	0.182 *** (5.255)	0.182 *** (5.263)
Elderly dependency		−0.006 *** (−3.186)	−0.006 *** (−3.280)	−0.006 *** (−3.273)
Illiterate population			−0.003 (−1.350)	−0.003 (−1.320)
Population aged ≥ 65				0.035 (0.938)
Constant	0.868 *** (114.986)	0.923 *** (48.460)	0.949 *** (35.510)	0.942 *** (34.110)
N	310	310	310	310
R2	0.076	0.108	0.114	0.117
F	22.772	16.837	11.865	9.115

Notes: *** indicates p < 0.01.

. They show that public health infrastructure and health equity are positively correlated at the 1% significance level across all four models, with the stepwise addition of the three control variables. This indicates that public health infrastructure is significantly associated with health equity, thereby confirming Hypothesis 1.

4.2. Robustness Test

4.2.1. Considering Endogeneity

Considering that the regression may generate endogeneity problems, we lag the explanatory variables by one period to reduce the endogeneity, following Ullah, et al. [66], Hill, et al. [67], and Reed [68]. Lagging the explanatory variables by one period takes into account the temporal relationship between the explained and explanatory variables while weakening the bidirectional relationship between them, which can reduce the bias in the model estimates.

Table 4. Results of the endogeneity test.

	Public Health Infrastructure	Health Equity
	(1)	(2)	(3)	(4)	(5)
L_Public health infrastructure	0.906 *** (26.479)	0.101 *** (4.334)	0.170 *** (4.966)	0.130 *** (3.859)	0.132 *** (3.927)
Elderly dependency			−0.005 *** (−2.730)	−0.005 *** (−3.101)	−0.005 *** (−3.136)
Illiterate population				−0.013 *** (−5.182)	−0.013 *** (−5.111)
Population aged ≥ 65					0.043 (1.090)
Constant	0.070 ***	0.873 ***	0.920 ***	1.014 ***	1.006 ***
	(6.265)	(114.980)	(49.158)	(39.884)	(37.969)
N	279	279	279	279	279
R2	0.739	0.071	0.098	0.187	0.191
F	701.126	18.783	13.365	18.799	14.407

Notes: “L_ Public health infrastructure” is the explanatory variable lagged by one period, *** indicates p < 0.01.

presents the results of the endogeneity test. It shows that public health infrastructure and health equity still show a positive correlation at the 1% significance level when the explanatory variables are taken one period afterward, which reaffirms the validity of Hypothesis 1.

4.2.2. Deleting Extreme Outliers

In China, unlike ordinary prefecture-level cities, the four municipalities, including Beijing, Tianjin, Shanghai, and Chongqing, have special characteristics in terms of economic development, political status, and population size, although they share the same administrative level as other provinces. Therefore, this study excludes these municipalities from the sample to test the robustness of the model by changing the sample size.

Table 5. Regression results with removing extreme outliers.

	Health Equity
	(1)	(2)	(3)	(4)
Public health infrastructure	0.112 *** (4.678)	0.273 *** (6.227)	0.266 *** (6.012)	0.266 *** (6.013)
Elderly dependency		−0.011 *** (−4.326)	−0.011 *** (−4.366)	−0.011 *** (−4.349)
Illiterate population			−0.003 (−1.183)	−0.003 (−1.157)
Population aged ≥ 65				0.035 (0.919)
Constant	0.859 ***	0.960 ***	0.984 ***	0.978 ***
	(105.691)	(38.980)	(30.671)	(29.731)
N	270	270	270	270
R2	0.083	0.149	0.154	0.157
F	21.883	21.098	14.554	11.120

Notes: *** indicates p < 0.01.

provides the regression results with the municipality sample excluded. The results show that the baseline regression model remains significant (at the 1% level) and consistent with previous findings.

4.3. Regional Heterogeneity

Given the variation in the level of economic development of different provinces, the effect of public health infrastructure on health equity is heterogeneous across provinces. In China, the provincial areas in the eastern region are economically developed, while the central and western regions are backward. As a result, this study divides the sample of provinces into eastern and central–western regions to implement group regression.

Table 6. Regional heterogeneity results.

	Health Equity
	Eastern	Central–Western
Public health infrastructure	0.005 (0.292)	0.305 *** (5.477)
Elderly dependency	0.000 (0.365)	−0.013 *** (−3.738)
Illiterate population	−0.001 (−0.281)	−0.003 (−0.994)
Population aged ≥ 65	0.039 ** (2.368)	0.029 (0.458)
Constant	0.948 ***	0.971 ***
	(66.642)	(21.205)
N	110	200
R2	0.064	0.174
F	1.632	9.276

Notes: *** indicates p < 0.01, ** indicates p < 0.05.

reveals that the effect of public health infrastructure on health equity is not significant in the eastern region but presents a significant effect in the central–western region.

4.4. Mechanism Tests

4.4.1. Mediating Effect

Table 7. Results of the mediation effect test.

	Hospitalization Utilization	Health Equity	Outpatient Utilization	Health Equity
	(1)		(2)
Public health infrastructure	9.621 *** (8.607)	0.145 *** (3.743)	1.181 *** (3.548)	0.160 *** (4.587)
Elderly dependency	0.186 *** (3.112)	−0.007 *** (−3.619)	0.056 *** (3.123)	−0.007 *** (−3.827)
Illiterate population	0.223 *** (2.671)	−0.004 (−1.641)	0.034 (1.370)	−0.004 (−1.585)
Population aged ≥ 65	−1.900 (−1.594)	0.042 (1.138)	−0.669 * (−1.883)	0.047 (1.289)
Hospitalization utilization		0.004 ** (2.075)
Outpatient utilization				0.019 *** (3.039)
Constant	8.325 ***	0.910 ***	4.126 ***	0.865 ***
	(9.315)	(28.901)	(15.504)	(23.211)
N	310	310	310	310
R2	0.537	0.131	0.275	0.146
F	79.827	8.241	26.057	9.358

Notes: *** indicates p < 0.01, ** indicates p < 0.05, and * indicates p < 0.10.

reports the results of the stepwise regression of the mediated effects model. In model (1), the coefficients of public health infrastructure and hospitalization utilization on health equity are significant at the 1% and 5% levels, respectively, indicating the presence of partial mediation effects. Similar to model (1), the coefficients of public health infrastructure and outpatient utilization on health equity are both significant at the 1% level, also showing partial mediation effects. Thus, Hypotheses 2a and 2b are validated. It is worth noting that compared to the correlation coefficient between public health infrastructure and outpatient utilization (1.181), the correlation coefficient between public health infrastructure and hospitalization utilization (9.621) is much larger, which suggests that public health infrastructure has a more favorable contribution to hospitalization utilization.

4.4.2. Moderating Effect

To address potential multicollinearity in the model, the interaction terms in this study are centered. The results in

Table 8. Results of moderation effect test.

	Health Equity
	(1)	(2)
Hospitalization utilization	0.008 *** (4.991)
Outpatient utilization		0.032 *** (4.583)
Health insurance	−0.034 ** (−2.520)	−0.040 *** (−2.909)
Hospitalization utilization × Health insurance	0.008 *** (3.103)
Outpatient utilization × Health insurance		−0.003 (−0.720)
Elderly dependency	−0.001 (−0.657)	0.001 (0.354)
Illiterate population	−0.004 (−1.365)	−0.004 (−1.585)
Population aged ≥ 65	0.071 * (1.925)	0.057 (1.516)
Constant	0.926 *** (28.670)	0.910 *** (29.040)
N	310	310
R2	0.141	0.108
F	7.470	5.536

Notes: *** indicates p < 0.01, ** indicates p < 0.05, and * indicates p < 0.10.

indicate that both hospitalization utilization and the interaction term “Hospitalization utilization × Health insurance” have a significant positive effect on health equity at the 1% level, suggesting that health insurance moderates the positive relationship between hospitalization utilization and health equity, confirming Hypothesis 3a. However, despite the significant effect of outpatient utilization on health equity, the interaction term “Outpatient utilization × Health insurance” is not significant on health equity, demonstrating the inability of health insurance to play a moderating role between outpatient utilization and health equity; therefore, Hypothesis 3b is not supported. This may be because outpatient reimbursement is lower than hospitalization reimbursement according to health insurance policies, as hospitalization usually involves higher medical costs, more complex procedures, and is more extensively covered than outpatient reimbursement.

5. Discussion and Conclusions

5.1. Discussion

Health equity is not only integral to sustainable development but also pivotal for fostering inclusive growth, social justice, resilience, and overall well-being on a global scale. By ensuring universal access to accessible, affordable, and high-quality health infrastructure and medical services, countries can advance sustainable development goals more effectively and create a healthier, more equitable world. In response to the significant attention to health equity from both governments and the academy, this study investigates the antecedents of health equity and the mechanisms to improve health equity. The results are presented in Figure 2.

Enlightened by the viewpoint that, like “cardiotonic agents”, high-quality public health infrastructure has a crucial effect on promoting health equity [3]. This study hypothesizes theoretically that health equity is significantly affected by public health infrastructure. Although the combination of maternal mortality rate and the mortality rate of infectious diseases of categories A and B reflects different dimensions of health equity, it must be acknowledged that the multidimensional concept of health equity cannot be completely covered. The paper also investigates how public health infrastructure influences health equity through the mediating effect of medical service utilization, including hospitalization utilization and outpatient utilization. Further, we consider health insurance as a moderating variable to explore its impact on the relationship between medical service utilization and health equity. It is worth emphasizing that the relationships observed in this study are statistically significant associations, and the low R² reveals the inability to account for factors such as spatial autocorrelation, unmeasured background variables, and dynamic processes in our analysis. Specifically, although VIF tests in Table 2 confirmed no multicollinearity, we recognize that spatial autocorrelation (e.g., diffusion of health policies between neighboring provinces) may persist. On the other hand, provincial-level data may mask sub-regional heterogeneity (e.g., urban–rural divides, ethnic disparities). For instance, grouping provinces in the central–western region aggregates areas with distinct socioeconomic profiles (e.g., Sichuan vs. Xinjiang), potentially obscuring localized dynamics.

Based on statistical data from 31 provincial administrative regions in China from 2011 to 2020, the empirical results suggest that public health infrastructure is significantly associated with health equity, although unmeasured contextual factors and spatial interdependence may play a key role. The finding responds to the current call from health equity research for more investigations into the antecedents of health equity [21]. Moreover, the research results differ from existing studies. Previous studies have reached inconsistent and even contradictory conclusions about the relationship between public health infrastructure and health equity. For example, Kristanto, et al. [11] found that the relationship between the availability of public health infrastructure and health equity was not significant in Indonesia. Valdivia [69] showed that while the development of public health infrastructure was vital, it was not sufficient to promote health equity among Peruvian adults. The reason for this difference is that China is widely promoting and expanding public health infrastructure across society through the implementation of various policies and laws, resulting in positive effects [10]. For example, in 2016, the State Council issued the “Healthy China 2030” Planning Outline, which pointed out that the medical and health industry should be built into a national pillar industry and strive to establish a high-quality and efficient public health infrastructure. In June 2020, “The Basic Medical Hygiene and Health Promotion Law of the People’s Republic of China” was implemented, focusing on advancing China’s medical and healthcare and trying to provide legal protection for citizens’ access to public health infrastructure. The construction and expansion of public health infrastructure promoted by the Chinese government allows every person to possess a fair and just opportunity to attain healthcare and improve their health.

Regarding regional heterogeneity, we find that the effect of public health infrastructure on health equity is not significant in the eastern region of China but presents a significant effect in the central–western region. The reason may be that the level of medical care in the central–western region lags behind that of the eastern region, lacking in resources such as medical facilities; therefore, increased investment in public health infrastructure positively enhances health equity. While the eastern region has developed economically, its medical resources are already rich enough that the increase in public health infrastructure investment can no longer support the effective upgrading of health equity. Moreover, the COVID-19 pandemic in China also revealed significant disparities in healthcare access and outcomes between urban and rural areas, as well as among different provinces. These disparities were exacerbated by the uneven distribution of public health infrastructure and medical resources, particularly in rural and western regions [12]. The pandemic underscored the need for a more equitable distribution of healthcare resources and the importance of strengthening public health infrastructure to improve health equity and societal resilience.

This study found that medical service utilization, including hospitalization utilization and outpatient utilization, partially mediates the relationship between public health infrastructure and health equity. The results address the limitations of previous studies. Existing research mainly investigates the relationship between medical service utilization and health equity [70,71], ignoring the mediating effect of medical service utilization between public health infrastructure and health equity. Public health infrastructure, such as the availability of hospitals, clinics, and healthcare providers, plays a crucial role in determining access to medical services. Regions with robust public health infrastructure are more likely to have greater access to medical services [72]. As a result, individuals in these regions may be more likely to utilize medical services, leading to better health outcomes and promoting health equity. At the same time, it cannot be ignored that medical service utilization alone may not fully explain the relationship between public health infrastructure and health equity. Other influencing factors, such as socioeconomic status, education, cultural factors, and structural determinants of health, also play important roles in explaining the relationship between public health infrastructure and health equity [73,74].

Moreover, the results reveal the significant effect of the moderating factor (i.e., health insurance) on the relationship between hospitalization utilization and health equity. It also shows that health insurance does not moderate the positive relationship between outpatient utilization and health equity. The results are different from previous studies to some extent. For example, Nandi and Schneider [75] showed that the development of publicly funded health insurance schemes, within the context of wider neoliberal policies promoting private-sector provisioning, had negative consequences for health equity and access. Anjorin, et al. [76] found that health insurance, especially community-based health insurance schemes, improved medical service utilization by disadvantaged groups; however, it was less likely to improve health equity. The difference may come from the fact that public health insurance and public medical services are the mainstay of the social security system in China. Since 2010, the Urban Employee Basic Medical Insurance, New Rural Cooperative Medical Scheme, and Urban Resident Basic Medical Insurance have almost achieved universal coverage in China. In addition to expanding health insurance, China launched a new round of reforms to its healthcare system in March 2009, including but not limited to improving basic health insurance benefits, promoting coverage of basic public health services, and advancing the hierarchical diagnosis and treatment system [70]. These reform measures have made significant progress in improving medical services utilization, health resource distribution, and health equity [77]. However, it is important to note that the New Rural Cooperative Medical Scheme and Urban Resident Basic Medical Insurance focus on reimbursement for hospitalization and catastrophic hospitalization expenses. This to some extent encourages rural and urban residents to utilize hospitalization services rather than outpatient services, contributing to a significant increase in hospitalization utilization. Additionally, the increase in population aging has also led to a rise in hospitalization utilization among older people. From the analysis above, we can find that establishing a robust health insurance system is increasingly imperative, as it can not only increase access to medical services, especially hospitalization utilization, but also improve health equity.

5.2. Contributions to Theory and Practice

The COVID-19 pandemic has also highlighted the importance of addressing health equity in the context of public health emergencies. This study unveils the “black box” between public health infrastructure and health equity based on statistical data from China. It can provide theoretical contributions to health equity research and practical implications for the government in promoting health equity.

5.2.1. Contributions to Theory

First, this study is among the early attempts to focus on health equity by exploring the effect of public health infrastructure on health equity, especially in promoting equity in the post-epidemic era. The COVID-19 pandemic has underscored the critical need for robust public health infrastructure to address health disparities and promote health equity, particularly in the context of large-scale public health crises [18]. The research results show that public health infrastructure is significantly associated with health equity when taking into account endogeneity and deleting extreme outliers, dealing with existing inconsistent and even contradictory conclusions. Second, the study promotes our knowledge of the mechanism to improve health equity considering the mediating effect of medical service utilization, including hospitalization utilization and outpatient utilization, and the moderating role of health insurance on the relationship between hospitalization utilization and health equity. These research findings could provide useful references for countries where public health infrastructure, public medical service, and public health insurance play leading roles in the entire medical system.

5.2.2. Contributions to Practice

This study offers significant practical insights for policymakers aiming to advance health equity across society. First and foremost, it is crucial to cultivate a robust public health infrastructure system. This encompasses medical personnel, equipment, and facilities, as well as adequate capital, all of which are vital for driving the healthcare industry forward. Public health infrastructure is the cornerstone for saving lives, enhancing societal well-being, and ensuring effective emergency response and disaster management during crises such as natural disasters, pandemics, accidents, or other emergencies. The COVID-19 pandemic has revealed the critical role of public health infrastructure in mitigating the impact of such crises, revealing that regions with stronger infrastructure were better equipped to manage the health and social consequences of the pandemic. In this context, hospitals, trauma centers, and emergency medical services must be well-equipped and strategically located to provide timely care, thereby mitigating the impact of disasters on public health. Moreover, public health infrastructure can positively influence regional innovation by boosting the natural population growth rate, improving educational levels, and increasing environmental greening [10].

Second, it is essential to address the imbalances in the regional distribution of public health infrastructure to achieve coordinated regional development. The regional heterogeneity analysis reveals that while the impact of public health infrastructure on health equity is not significant in the eastern region of China, it is pronounced in the central–western region. This finding underscores the need to acknowledge the disparities in social, economic, and environmental contexts between regions when examining the relationship between public health infrastructure and health equity. To reduce these disparities, policymakers should focus on targeted investments in public health infrastructure in less developed areas, ensuring that resources are allocated equitably. Some potential measures can be considered, for example, (1) increasing the government’s financial investment in the construction of public health infrastructure in the central–western region, while optimizing its regional planning and resource allocation; (2) upgrading the quality and accessibility of public health services in the central–western region, i.e., implementing a targeted training program to bring in relevant talents for the central–western region and further strengthening the standardization and informatization of grassroots healthcare institutions; and (3) establishing a mechanism for medical and healthcare counterpart support between the eastern region and the central–western region to promote the development of medical and healthcare in the central–western region through technical assistance, talent training, and resource sharing.

Third, it is imperative to enhance reimbursement management within the health insurance system. The research findings indicate that, compared with outpatient utilization, health insurance has a moderating effect on the relationship between hospitalization utilization and health equity. This may stem from the fact that hospitalization reimbursement rates are generally higher than outpatient reimbursement rates, which could lead to unnecessary hospitalizations and the wastage of medical resources. To address this issue, it is necessary to rationalize the reimbursement rates for both hospitalization treatment and outpatient visits. This should involve a careful review of current reimbursement policies to identify areas where adjustments can be made to minimize inefficiencies and promote more equitable access to healthcare services. Policymakers should also consider the broader social and economic context when making these adjustments, ensuring that they do not disproportionately affect vulnerable populations. For instance, measures should be taken to protect low-income individuals and families from financial barriers to accessing necessary medical care, whether it be through increased subsidies, sliding-scale payment plans, or other targeted interventions.

In addition to these recommendations, it is important to recognize that health equity is deeply intertwined with broader social and economic inequalities. The COVID-19 pandemic has further highlighted these interconnections, revealing that health disparities are often exacerbated by underlying social and economic inequalities [19]. Therefore, efforts to improve public health infrastructure and health insurance reimbursement policies should be complemented by comprehensive strategies aimed at addressing the underlying determinants of health. This includes initiatives to reduce poverty, improve education and employment opportunities, enhance housing conditions, and promote social inclusion. By taking a holistic approach that addresses both the immediate healthcare needs and the broader social determinants of health, policymakers can create a more equitable society where all individuals have the opportunity to achieve and maintain good health.

5.3. Limitations and Future Work

This study does not exclude limitations. First, this study mainly adopts two indicators of maternal mortality rate and the mortality rate of infectious diseases of categories A and B to present health equity. However, it should be clarified that health equity is an index with a multidimensional concept and these two indicators may not cover all aspects. Therefore, in future studies, an attempt could be made to extend it to a wider range of morbidity/mortality indicators (e.g., population mortality, infant mortality) to comprehensively compare them to better capture this complex concept.

Second, the health insurance variable is reflected by the logarithmic value of the per capita basic health insurance fund expenditures, which could not be specifically explored in this study. Future studies could compare different types of health insurance (public vs. private, or different schemes within China), or assess whether the level of coverage (quantitative) affects access to basic versus specialized services differently.

Third, despite the statistical significance of our findings, the low R² also suggests that some underlying factors (e.g., spatial autocorrelation) may have contributed to the existence of such unexplained variances. Thus, future research could combine these models with complementary qualitative or mixed methods. For example, on the one hand, future work could apply spatial econometric techniques (e.g., spatial lag models, Moran’s I) to explain geographic interdependence; on the other hand, it could integrate county-level data or urban–rural stratification to bridge sub-provincial gaps.