This survey was conducted among older adults permanently residing in rural areas of China during July and August 2024. Given the extensive geographic scope, along with practical constraints related to time, funding, and varying levels of digital literacy among the older adult population, the study used the Credamo online data platform for randomized questionnaire distribution. To overcome challenges associated with self-reporting, particularly among very old or socially isolated individuals, and to enhance sample representativeness while minimizing bias, a proxy-response method was adopted, whereby adult children provided responses on behalf of their parents. All participants were required to answer every item in the questionnaire.

To ensure the smooth implementation of the online survey, a two-phase survey approach was adopted. In the first phase, we conducted field visits to five villages, collected over 50 questionnaire responses, and held face-to-face discussions with multiple older adults and their children. Based on the feedback received, the questionnaire was refined and optimized through multiple rounds of revisions to ensure clear and comprehensible wording of the questions, to enhance its appropriateness for the target population, and to establish a solid foundation for the validity of proxy-completed questionnaires by adult children. The second phase involved the formal survey. Eligibility criteria included respondents aged 60 years or older, proxies possessing comprehensive knowledge of their parents’ health status, and long-term residence in rural areas. Sample size was determined using the Kendall method, which recommends 10 to 20 observations per variable (22). Accounting for an anticipated 10% attrition rate, the target sample size was set between 200 and 400 participants. To ensure data quality, several filtering mechanisms were implemented, including IP address verification and account restrictions to prevent duplicate entries. Additional checks excluded responses with completion times under 5 min or those exhibiting logical inconsistencies. From an initial pool of 501 collected questionnaires, 103 were excluded due to overly rapid completion, missing data, or failure to meet residency or age criteria, resulting in 398 valid responses for analysis. Statistical analysis confirmed that the sample was well-distributed geographically, supporting its randomness and indicating successful mitigation of selection bias.

This study received ethical review and approval from the Ethics Committee of The First Affiliated Hospital of Air Force Medical University (Xijing Hospital) (approval no: KY20252074-C-1). Prior to survey administration, informed consent was obtained from all participants after a comprehensive explanation of the study objectives. Explicit assurances were provided regarding data confidentiality, and privacy protection measures were implemented in accordance with ethical standards for research. Following data collection, all data were processed and analyzed using SPSS software.

To examine the impact of primary healthcare accessibility on health vulnerability, a structural equation model (SEM) was developed to evaluate its effects on both physiological and psychological vulnerability. In contrast to traditional regression models, SEM allows for the examination of complex causal relationships between latent and observed variables through path analysis. The structural segment of the model depicts the relationships among latent variables, while the measurement component specifies the linkages between latent variables and their manifest indicators. The SEM is formulated as follows:

η is the two dependent variables: physiological and psychological vulnerability, ξ is two independent variables. β represents the structural coefficient of the relationship between two latent variables, and Γ represents the structural coefficient of the relationship between latent variables and the explanatory latent variable. ζ represents the prediction error (disturbance term) in the structural model. Meanwhile, we used multi-group SEM to test for heterogeneity. Multi-group SEM can be used to test whether the path coefficients are invariant across different subgroups.

Furthermore, to estimate the loading coefficients between latent and observed variables, we used AMOS 20.0 for constructing and evaluating the SEM, specifically to analyze the influence of primary healthcare accessibility on health vulnerability among older adults.

Our final sample included a total of 398 older adults. Table 2 shows the characteristics of each participant. The number of male participants was about the same as that of female participants. The majority of participants were married. Specifically, the average age of the respondents was 70.1 years. The percentage of female participants was 54.8%, and that of male participants was 45.2%. There were fewer older people with no formal education, accounting for only 3.0%. Older people were living alone, accounting for 13.1% of the sample. There was no income accounting for 12.3%.

Table 3 summarizes the level of participants’ health vulnerability. On average, the level of physiological vulnerability is above 0.40, presenting a higher score than psychological vulnerability. The highest standard deviation (SD) of psychological vulnerability among the three variables shows the discrepancies in the data. When using the frailty index as an assessment criterion, older adults with scores below 0.25 are classified as having a low level of health frailty, while those with scores equal to or greater than 0.25 are identified as having a high level of health frailty (23). Overall, the level of health vulnerability is above 0.40, suggesting that older adults have some health vulnerability problems to some extent.

Table 3 also reports access to primary healthcare services. The average score of geographical accessibility is above 2.40, the average score for quality is below 0.80, and the average score of financial accessibility is below 4.00. The score indicates that the geographical accessibility is the best among the three measured variables, with an overall level that is higher. Furthermore, access to township health clinics is better than village healthcare centers.

The study found a comprehensive health vulnerability index of 0.42 among older adults, with physical and mental health sub-indices measured at 0.44 and 0.27, respectively. All values surpassed the internationally recognized threshold of 0.25 (23), indicating considerable health vulnerability within this population, a result consistent with prior studies (27). Health in older adults can be characterized as a dynamic process of progressive decline associated with aging (28). Common issues such as sedentary behavior, insufficient physical activity, weakened immune function, and a tendency to disregard atypical symptoms or delay medical consultation contribute to the persistence and exacerbation of health vulnerability. As physiological capacity diminishes, older adults frequently experience mental health challenges related to perceived loss and aging, which can provoke negative emotions and intensify psychological vulnerability (9). This psychological vulnerability may, in turn, adversely affect physical health. Older adults, who exhibit high rates of chronic disease and comorbidities (29), often face limitations in activities of daily living due to health impairments. This increases their reliance on family and primary healthcare services, a dependent status that can evoke feelings of guilt or perceived burden, thereby indirectly worsening psychological vulnerability (30). To reduce health vulnerability, several measures should be implemented: actively addressing unhealthy behaviors, maintaining regular physical activity (31), participating in periodic health screenings, and cultivating personal interests and social engagement to strengthen psychological resilience (32). Together, these strategies can alleviate vulnerability across both physical and mental domains, establish a virtuous cycle of health, and ultimately enhance quality of life in later years.

Among the three dimensions of primary healthcare accessibility—geographic, quality-related, and economic—economic accessibility demonstrated the most prominent performance and was consistently maintained at a relatively high level. This can be largely attributed to sustained socioeconomic development and the Chinese government’s vigorous promotion of the basic medical insurance system, which has effectively reduced the financial burden of healthcare on residents (33). Township health centers showed significantly better comprehensive accessibility compared to village clinics, consistent with existing research (34), which may be explained by more equitable resource allocation at the township level (35). Village clinics, which represent the most grassroots yet vulnerable tier of the rural health system, face critical shortages in medical equipment and healthcare personnel. These constraints limit their capacity to meet the diverse, long-term, and comprehensive medical needs of older adults. Moreover, certain medications are not covered by insurance at village clinics, leading many older adults to seek care at township health centers instead. Nevertheless, as the “last kilometer” of healthcare for rural residents, village clinics provide unique advantages in geographic proximity and continuity of patient–provider relationships, enabling more timely and personalized care (36). Thus, they play an indispensable role in enhancing health service accessibility. In the context of China’s health-first strategy and the introduction of multiple supporting policies for primary healthcare development, it is imperative to leverage government initiatives to systematically strengthen village clinics. Efforts should focus on optimizing the allocation of primary medical resources and enhancing the service capacity of primary care institutions. These measures will help solidify the role of village clinics as “health gatekeepers,” reinforce their foundational functions in prevention, diagnosis, treatment, referral, and health education, and tangibly improve the effectiveness of healthcare support for rural residents.

The heterogeneity of demographic variables in the relationship between access to primary healthcare services and vulnerability to health. First, regarding gender differences, the impact of primary healthcare accessibility on health vulnerability was significantly more pronounced among older women than among men. This disparity may be attributed to several factors: women tend to utilize healthcare services more frequently, translate health knowledge into practical behaviors more effectively (37, 38), exhibit greater sensitivity to health risks, and engage more proactively in health self-monitoring (39). They also generally demonstrate higher adherence to medical advice compared to men (40). In contrast, men often pay less attention to health maintenance. Furthermore, older women tend to experience a lower ratio of healthy life expectancy relative to total remaining life expectancy. As a result, healthcare services, which facilitate the transition from unhealthy to healthy states, produce a more substantial marginal effect on health outcomes among older women. As noted by scholar Wei Yan (41), comprehensive medical security and effective disease prevention significantly reduce health poverty vulnerability among rural women, a finding that aligns with and reinforces this study’s result that women benefit more markedly from primary healthcare accessibility. Second, in terms of educational attainment, varying levels of education moderated the effect of primary healthcare accessibility on health vulnerability. Compared to the intermediate education group, both the low and high education groups showed weaker effects on mental health vulnerability. Older adults with low educational levels generally possess a limited capacity to acquire and utilize health information (42). They often seek care at village clinics only for physical symptoms and tend to neglect mental health issues, compounded by generally low health literacy. On the other hand, although highly educated individuals have better health literacy, they often exhibit relatively low trust in primary healthcare services. In addition, the limited capacity of village clinics to provide professional psychological support further attenuates the effect of primary healthcare accessibility on psychological vulnerability in both groups. Third, marital status also significantly moderated the relationship between primary healthcare accessibility and health vulnerability. This may be because married individuals generally benefit from more stable economic conditions, allowing them to seek healthcare without major financial constraints, while a sense of familial responsibility motivates more proactive use of health services (43, 44).

Finally, analysis based on living arrangements indicated that the influence of primary healthcare accessibility on health vulnerability was more pronounced among older adults living with family members, while this association was not statistically significant among those living alone. This finding contrasts with the results reported by Zheng Jiyou et al. in their study on rural empty-nest older adults, which identified healthcare accessibility as a significant factor affecting the health of older adults living alone (45). The discrepancy may be related to methodological differences. The current study relied on proxy questionnaires completed by adult children on behalf of their parents. Although respondents were instructed to accurately report their parents’ health status, children cohabiting with parents likely had more frequent daily interactions and were therefore better informed about their parents’ health conditions. In addition, older adults living with family receive more daily companionship and health-related monitoring, leading to greater health awareness and higher healthcare utilization. Thus, the effect of primary healthcare accessibility appeared more evident in this group. In contrast, older adults living alone often lack regular companionship and health reminders, increasing the likelihood of overlooking mild symptoms or delaying medical consultations. This behavior can allow minor health issues to progress into serious conditions. In such contexts, conventional primary healthcare services may be insufficient to effectively address their needs, which may explain the attenuated role of accessibility in this subgroup. We recognize certain limitations regarding the representation of older adults living alone in this study. Therefore, we emphasize that findings related to this group are preliminary and based on the available sample. Generalizability should be further verified using more diverse research methods in future studies. We avoid over interpreting these results and focus instead on elucidating the relationships between variables. Existing research consistently demonstrates that older adults living alone, often affected by insufficient social support, loneliness, and elevated depression risk (42, 46), exhibit particularly high health vulnerability. The study by Yan Yueping et al. (47) further highlights that depressive mood is the most severe health issue in this population, directly aggravating their mental health vulnerability. Thus, this study suggests that for older adults living alone, social conditions may exert a stronger influence on health vulnerability than primary healthcare accessibility. What is most needed in this group is robust social support and targeted psychological intervention.

In summary, primary healthcare services are well-suited to the health needs of older adults due to their core attributes of accessibility, continuity, and comprehensiveness. As the first line of defense within the healthcare system, primary healthcare plays a vital role in improving health literacy among older adults. It facilitates early detection of health issues and enables timely referrals when necessary, thereby effectively preventing disease progression and reducing the risk of complications (48). For older adults requiring long-term care, primary healthcare institutions can deliver continuous and integrated services by coordinating resources from families, communities, and institutional providers (49). The government should adopt a multidimensional approach to enhance the capacity and accessibility of primary healthcare, with emphasis placed on the following priorities: strengthening resource allocation to village clinics, implementing systematic training programs for village doctors, upgrading age-friendly infrastructure, and expanding health education initiatives at the grassroots level. Particular attention should be directed toward vulnerable groups, including older adults and women (37). Basic medical insurance policies should also be optimized to reduce the financial burden of healthcare on older adults. Through these measures, disparities in primary healthcare accessibility can be diminished, health vulnerability among older adults can be mitigated, and healthy aging can be effectively promoted.