Background
China is undergoing unprecedented social change. An increasing number of people leave their original places of residence to work and live in other provinces or cities to improve their lives. Such people are called internal migrants. According to the National Health Commission, the Chinese migrant population exceeded 240 million in 2017 [
1]. In 2009, China initiated the National Essential Public Health Services (NEPHS) project [
2]. It is the NEPHS that the government provides free of charge to all residents in view of the main health problems existing in urban and rural residents, with children, pregnant women, the elderly and patients with chronic diseases as the key groups. Due to the restrictions of household registration system, the migrants is at a disadvantage in accessing NEPHS in their destinations [
3,
4]. In 2013, the central government reintroduced measures to promote NEPHS equalization of internal migrants, and since then, NEPHS deployment level has risen rapidly [
5,
6]. However, there is still a significant gap in the national planning target [
3,
4,
7]. Thus, evaluation of the factors affecting the continuous improvement of the NEPHS utilization by internal migrants and their mechanism of action has become a significant concern that needs immediate resolution.
Social capital refers to the resources and benefits received through connections with others, either as individuals or groups [
8]. Social capital is an important social determinant of health, and access to health services has been suggested as a pathway by which Social capital influences health outcomes [
9]. The pathways in which social capital influences service accessibility are as follows: (1) promoting the sharing of information among neighbors; (2) changing health behaviors, attitudes, and concepts through interaction with peers [
10‐
12]. Migration means a loss of the original social network and a disruption in civic participation in the new environment [
13], which results in the deficiency of the localized social capital of the migrants. Compared with the local population, the social capital of migrants in the destination areas also shows a considerable deficit [
14,
15] and is associated with various adverse health outcomes [
16‐
22].
Social capital can be divided into different dimensions (cognitive and structural) and different levels (community and individual). Different types of Social capital affect health services utilization by influencing the availability of health services in communities, the availability and effectiveness of outreach resources between health-care providers and communities they serve, and care-seeking behavior of individuals in those communities [
23]. However, Uphoff et al. [
24] pointed out that not everyone has access to the same sources of social capital and not everyone will benefit in the same way, they proposed three paths by which Socioeconomic status (SES) could affect the relationship between social capital and health outcomes. (1) A more significant social capital benefit on the health of disadvantaged persons in the society, and no effects or limited health benefits for those in positions higher up in the social ladder. (2) People with a low SES will generally have less social capital, and the capital available to them cannot be used effectively for health benefits. (3) Social capital might benefit the better-off in society while excluding people with a lower SES or a minority position.
In some high income countries, the lack of social capital is reported to significantly limit the effective utilization of local health services by migrant populations [
10,
11]. However, due to the interdependence of cultural, economic, and social capital [
25], the relationship between social capital and health is not consistent across countries [
26,
27]. Notably, the social capital of Chinese people has unique characteristics, with a higher level of trust and a lower level of social participation [
28]. The association between social capital and health also presents substantial uniqueness in China [
22,
29]. Therefore, it is necessary to continually explore the correlation between social capital and health in the migrant population. However, these previous studies focused more on the health outcomes and neglected the process by which migrants access NEPHS in their destination regions. The study by Hou et al. [
30] was an exception, they confirmed the positive effect of individual structural social capital on the health education acceptance and health record establishment of the migrant population.
There are currently at least three unclear dimensions on the relationship between social capital and NEPHS utilization among the Chinese migrants that need further exploration: (1) The influence of different dimensions of individual social capital, both cognitive and structural, on the health outcomes [
8]. Although the effect of the latter (structural social capital) on NEPHS utilization has been verified [
30], the effect of the former is unclear. (2) The effects of different levels of social capital, both individual and contextual, on the health outcomes [
8]. Most studies [
22,
30] on the relationship between social capital and NEPHS utilization by migrants were conducted at the individual level, and the discussion was deficient at the contextual level. (3) Differences in the application of social capital and NEPHS by the different migrant population subgroups. The differences in the relationship between social capital and health among different subgroups have attracted increased research attention and could constitute the future focus of social capital [
31]. The differences in this relationship between different subgroups of the Chinese migrant population also need to be explored.
In the context of China, a huge low-middle income country (LMIC), this study takes the internal migrants as the respondents to answer three questions: (1) What are the distribution characteristics of individual social capital and NEPHS utilization level among migrant population subgroups with different sex and education levels? (2) How do different dimensions (cognition and structure) and different levels (individual and contextual) of social capital affect the utilization of NEPHS? (3) Do sex and education significantly moderate the relationship between social capital and migrant population NEPHS utilization? The answers to three questions will help us understand the mechanism of social capital on the NEPHS utilization by internal migrants. This will not only help the Chinese government to better promote relevant work, but also provide a meaningful reference for other countries, especially LMICs, to promote the equalization of public health services for the migrants.
Discussion
There were three main findings. (1) There are significant differences in the levels of CSC, SSC, and NEPHS utilization between different sexs and educational subgroups of the migrants, among which differences in education years are more prominent. (2) An Interaction exists between the levels and dimensions of social capital and NEPHS projects; the effect of SSC on the NEPHS is always greater than that of CSC at the same level. (3) The effects of RCSC, RSSC, ICSC, and ISSC on NEPHS utilization of migrants are not moderated by sex. However, a higher education could weaken the relationship between RCSC and health education, strengthen the link between RSSC and health education, weaken the relationship between ISSC and health education, and also weaken the association between RSSC and health records.
As some studies have pointed out, the social capital of China’s migrant population is insufficient [
14,
15]. However, according to the data in this study, this deficiency may only exist in SSC, and the level of CSC of the Chinese migrant population is still high. Lack of economic and cultural capital bars societal subgroups from acquiring and using social capital [
25]. People with high SES have advantages in the acquisition of social capital [
24], which is also true for Chinese migrants [
19,
34], a fact also confirmed in this study from the gap of social capital in education. A Canadian survey found that men’s CSC was lower while the SSC was higher than that of women [
22] . In China, a survey of migrants in Wuhan, Hubei province, did not find sex differences in social capital [
19]. Another survey in Shaoxing, Zhejiang province, also found no significant sex difference in social trust and social participation [
34]. The sample and different operational definition of social capital could account for the inconsistency. CSC can be divided into generalized and particularized trust [
32], the Canadian and Hubei studies used generalized trust, while the Zhejiang study investigated particularized trust (trust to local people). For SSC, it is difficult to compare different studies due to the large differences in the included contents. The concept of CSC and SSC in this study is more similar to that in the Zhejiang, we found that the differences of sex in CSC and SSC, while statistically significant, were small. Which needs to be verified in future studies under a unified concept. As for the sex and education differences in health education and health records, the conclusions of this study are similar to previous studies [
3,
5,
6,
35,
36].
Poortinga [
26] analysed data from 22 European countries and concluded that individual-level rather than context-level (states) social capital is associated with self-rated health. A similar study in rural China found that CSC, at both individual and contextual (village) levels, is positively correlated with health. Meanwhile, SSC has very low statistical association at both levels [
28]. These two studies [
26,
28] concur on the ICSC, similar to this study. This study demonstrated that ISSC is positively related to NEPHS, which is also consistent with similar studies [
30]. According to Palmer et al. [
14], the overall level of social participation in rural China is considerably low, which attributed to the flooring effect [
28]. Of note, the bulk of the migrant population is farmer, most of who live in cities, and the social participation of cities is higher than that of rural areas [
14]. Awareness is a prerequisite to NEPHS access, and lack of awareness is the main obstacle hindering the utilization of NEPHS by migrant population [
37]. Besides, the information function of SSC makes service acquisition a more useful resource for NEPHS. It is worth noting that in this study, RSSC is the most prominent factor affecting the NEPHS, and the effect of RCSC on NEPHS is more complicated. As a government project, NEPHS are more affected by government input. Zhang et al. [
6] reported that investment to NEPHS varies among different regions of China. Therefore, social capital at contextual (provinces) level may have a more significant impact on NEPHS. The relationship between RSSC and NEPHS reflected this correlation, but RCSC only had a significant impact on health records. This may be because health education only needs pure information exposure, so information (SSC) is more important. The establishment of health records also requires active cooperation, so recognition (CSC) is more important.
Studies based on the western background reveal sex differences in the relationship between social capital and health outcomes [
32,
38‐
40]. However, this study did not observe any sex difference, which could be attributed to the uniqueness of the Chinese social capital but needs further investigation. In the background of this paper, we mentioned that Uphoff et al. [
24] proposed three paths by which SES could affect the relationship between social capital and health outcomes. Based on the analysis results of this study, we infer that: the relationship between education, RCSC, ISSC, and health education conformed to path 1, while the relationship between education, RSSC, and health education conformed to path 2. In particular, this study found that the relationship between education, RCSC, and health records did not correspond to either path and appeared as an aggressive version of path 1. We can speculate that the dimensions and levels of social capital, education, and the types of NEPHS projects jointly affect the utilization level of NEPHS by the migrants in the destination. In summary, the data showed that low-education migrants benefit more from RCSC when accessing NEPHS. This suggests that the local government should attach great importance to improving the local identity of the migrant population when promoting the equalization of NEPHS.
Two problems need to be pointed out. Firstly, this study simplifies health education by merging the nine health education items into one and dualizing the options for “yes or no”. This evaluation criterion is based on the premise that each province attaches equal importance to the nine health education items. In fact, different provinces have different concerns about the health of the migrant population [
41], which will affect their choice of health education content and the acceptance rate of the same health education program by the migrants also differs significantly among the provinces [
6]. Although the simplified criterion is convenient for overall comparison, it may cause bias in results interpretation. Secondly, as mentioned by Palmer et al. [
17], the social capital of Chinese people has its own characteristics, and the cultural difference is more prominent in SSC. Although the measurement indicators of social capital in this study are based on the Chinese cultural background, the mechanism of its influence on public health services is universal, so the conclusion of this study still has certain reference value for other countries.
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