Globally, non-communicable chronic (NCDs) diseases have become the leading cause of disease burden. Recently, cardiovascular diseases (CVDs) refer to ischemic or hemorrhagic diseases of the heart, brain, and body caused by factors such as hyperlipidemia, blood viscosity, atherosclerosis, and hypertension, which have the highest mortality rate among NCDs. (1, 2) In China, CVDs were major contributor to the burden of disease, which have caused serious damage to the health of people and the economy. (3) It has previously been noted that the age-standardized prevalence of CVDs in China increased significantly by 14.7% overall, and the number of deaths caused by CVD increased from 2.51 million to 3.97 million, from 1990 to 2016. CVDs account for more than 40% of deaths in China. Compared with cities, the mortality rate in rural areas is higher. In 2016, the mortality rate of CVDs in rural China was 309.33 per 100,000, and 158.15 per 100,000 for cerebrovascular diseases. (4) Most of the risk of CVDs is attributable to relatively few and modifiable risk factors, such as lifestyle, diet, economic status. (5)

Carbon productivity is a composite indicator that takes into account both carbon emissions and economic output. A higher carbon productivity value signifies that more economic output is achieved while emitting less carbon, which is seen as a positive result of reducing the environmental impact of carbon emissions. (6) People’s health could be affected by the carbon productivity of the area where they live, as higher levels of carbon emissions can have negative impacts on human health. Carbon emissions from human activities, such as the burning of fossil fuels, contribute to air pollution, which can have serious health consequences. (7) Numerous studies have shown that air pollution is an independent risk factor for CVDs. (8, 9) The risk of CVDs increases by 0.27% for every 10 mg/m³ increase in the average daily PM_2.5 concentration in China. (10) In addition, the increasing carbon emission has caused the “greenhouse effect” to be responsible for global warming in the past decades. (11) In the context of global warming, cardiovascular hospitalizations will likely increase. (12) Carbon productivity could be a promising metric for evaluating the environmental health of a region. However, there is a scarcity of research on the association between carbon productivity and health outcomes. Further studies are needed to establish a clearer understanding of the association.

Considerable research has examined the relationship between socioeconomics, medical resources and the risk for CVDs from the individuals’ perspective. (13, 14) In rural China, people in lower socioeconomic status groups are more likely to have a higher risk of CVDs (15), which is driven by a range of factors, including education, air pollution, and unhealthy lifestyles. Besides, people from low socioeconomic backgrounds are less likely to have access to adequate medical resources, including preventive services, diagnostic tests, and treatment options, which can help to identify and manage CVDs risk. (16) However, studies of spatial analysis to explore the spatial heterogeneity of these associations are limited, which has advantages for developing regional development plans and efficiently allocating medical resources to maximize benefits for the population.

Recently, geographically weighted regression (GWR) model parameter estimation algorithms have been continuously improved. (17–19) The GWR model provides an intuitive and practical method for spatial analysis of heterogeneity of spatial relationships, which has gradually become an effective approach to exploring the spatial association of disease burden with influencing factors, thus providing a basis for the government to formulate health policies or allocate medical resources rationally. (20–22) Additional studies are needed, as kinds of spatial analysis studies are limited in the field of CVDs.

Fujian is a representative province in the southeastern coastal area of China, comprising 84 counties with a population of about 39 million and an area of 121,400 km². Our previous study found that the number of rural elderly inpatients with CVDs in southeastern China is increasing rapidly, and CVDs were the main cause of catastrophic medical expenses. (23) Thus, this study aimed to further describe the temporal and spatial distribution pattern of CVDs hospitalizations, and to explore the relationship between carbon productivity, socioeconomics, medical resources and hospitalization for CVDs by spatial analysis. The findings are essential for the government to formulate health policies, improve economic development plans, and allocate medical resources rationally to cope with the disease burden of CVDs.

This study has comprehensively explored the characteristics of rural inpatients with CVDs in southeast China by sex, age, and spatiotemporal distribution. We observed that the number of rural inpatients with CVDs had been rising dramatically. Essential hypertension, cerebral infarction, and chronic ischemic heart disease were the leading causes of hospitalization. In addition, to the best of our knowledge, this is the first spatial analysis study to assess the association between carbon productivity (CP) and health outcomes. We observed that CVDs hospitalization rates were negatively associated with CP, and positively associated with per capita GDP (PGDP) and hospital beds per 10,000 population (HB) in most counties.

We observed that the number of rural inpatients with CVDs had increased by 95.29% from 2010 to 2016. The majority of inpatients were elderly. Cardiac arrest, transient ischemic attack and related syndromes had the highest average percentage change rate. The fast-growing inpatients with CVDs was possibly related to the development of Chinese society and the intensification of aging problems, changes in people’s lifestyles, and medical and health care. Consistently, relevant studies had pointed out that with the aging process of Chinese society in the 21st century, the prevalence and incidence of age-related diseases have risen sharply. (39) Higher age was an independent risk factor for CVDs. Among age-related diseases, CVDs represented by heart disease and cerebral infarction are the main causes of death. (40, 41) In addition, after China’s long-term construction of the medical system, more rural residents have access to medical services, which may also be the reason for the increase of CVDs inpatients. (24, 42)

In our study, the number of female inpatients for CVDs was higher than male. Previous studies used to consider CVDs as a male-predominant disease. (43) However, CVDs were also the leading cause of death and loss of disability-adjusted life years for women worldwide. (44) This phenomenon may be attributed to insufficient attention to the prevention of CVDs in women. Studies have shown that in the United States, compared with men, women with CVDs were more likely to be underdiagnosed and not receive preventive care or appropriate treatment. (45) In China, women place less emphasis on primary and secondary prevention of CVDs than men, who may experience heart disease in different ways, and lack of awareness of it, which had been revealed to lead to adverse outcomes. (46, 47) Therefore, it is necessary to redefine the meaning of women’s health to cover the entire life cycle, with more emphasis on the prevention of CVDs and other non-communicable diseases.

We observed that the hospitalization rates for rural inpatients with CVDs were not discretely distributed in southeast China, but exhibit obvious aggregated in central and midwestern counties, such as Meilie, Sanyuan, Mingxi, Jiangle, and Shaxian. Consistently, the distribution of CVDs burden varies greatly different in regions of China. Coastal provinces with higher economic development have a lower CVDs burden than inland regions, and northern regions with more severe air pollution are higher than southern regions. (8, 48) Therefore, to achieve higher health policy benefits, it is suggested that the government should formulate targeted health policies to reduce the CVDs burden based on the multi-dimensional characteristics of each county such as economy, health resources, population, and CVDs burden.

We found that higher CP was negatively associated with the hospitalization rate of CVDs, while PGDP was positively associated with them. These correlations were stronger in central and midwestern counties. These results suggest that low-carbon development is beneficial in reducing the burden of CVDs. The abusive and inefficient use of non-renewable energy may improve the regional economy in the short term, but the cost is the emission of a large amount of greenhouse gases, resulting in air pollution and destruction of soil and water quality, and ultimately lead to an increase in the burden of CVDs. (8–10, 12) In study area, the central and midwestern counties were economically underdeveloped regions, there may exist a large number of inefficient and highly polluting industries and technologies, resulting in massive carbon emissions and environmental pollution. In order to mitigate the disease burden of CVDs, it is imperative for the government to promote a balance between economic development and environmental protection. We recommend implementing policies such as carbon trading, (49) promoting renewable energy, (50) rationally adjusting the industrial structure, (51) and reducing reliance on fossil fuels. Such measures can not only help reduce carbon emissions, but also have the potential to improve public health, promote economic development and reduce the incidence of CVDs.

We observed that there was a stronger positive association between proportion of low-income households (PLIH) and hospitalization rate of heart diseases and cerebrovascular diseases in central and the western parts. Consistently, research had shown that poverty is a risk factor for CVDs. (52, 53) Low-income households were more likely to be unable to afford primary and secondary prevention services for CVDs, leading to disease progression and ultimately hospitalization. Therefore, in central and the western counties need to pay more attention to the problem of the gap between the rich and the poor. On the other hand, it is worth considering increasing the coverage of public medical insurance and the reimbursement ratio of medical expenses for the poor. (54)

We found that HB had a positive function on the hospitalization rate of CVDs, especially in the northern and central counties. The results indicate a significant imbalance in the distribution of medical resources in the southeast rural China. Consistently, Previous studies have suggested that the distribution of health resources in Fujian mainly concentrated in economically developed regions like Fuzhou, Xiamen, Quanzhou, and other coastal areas, while health resources are scarce in the northern. (23) With the Health-Care Reforms in China, rural residents can receive medical services more conveniently, (24, 42) which promotes an increase in the number of hospitalizations. However, the uneven distribution of medical resources is still an issue. (55, 56) In some counties, the increase in medical and health resources may not be sufficient to meet the health needs of the population, leading to difficulties and delays in seeking medical treatment. In contrast, other areas may have sufficient medical and health resources, and further increasing resources may not significantly increase the number of patients seeking medical treatment. Therefore, in order to better meet the health needs of the population, China’s healthcare system still needs further improvement, especially in underdeveloped inland areas. More rational allocation of medical and health resources is a key step in achieving this goal.

Our study has several limitations that should be noted. Firstly, medical insurance policies can vary between counties based on their financial situation, potentially affecting the hospitalization rates of rural residents with CVDs. Second, the NRCMS database only records the main diagnoses of inpatients, while many patients often have multiple diseases simultaneously, which may lead to an underestimation of the number of hospitalizations due to CVDs. Thirdly, the NRCMS is a healthcare insurance policy for rural China, and all study participants are exclusively rural residents. Therefore, caution should be exercised when extrapolating the study’s results to urban areas due to significant differences in demographic and environmental characteristics. Finally, our study is subject to the risk of ecological fallacies as it was conducted at the county level. To mitigate this limitation, future research using individual-level data would be beneficial to validate our findings and assess their generalizability.

The number of rural inpatients with CVDs had been rising dramatically. The main groups affected were elderly and women, with essential hypertension, cerebral infarction, and chronic ischemic heart disease were the leading causes of hospitalization. In addition, the CVDs hospitalization rates were negatively associated with CP, and positively associated with PGDP and HB in most counties. The association between CVDs hospitalization rates and CP and per capita GDP was stronger in central and midwestern counties, while the association with HB was stronger in northern counties. Based on our findings, we recommend taking the following measures to address the increasing inpatients with CVDs. First, conducting more CVDs prevention work in rural areas, particularly in central and midwestern counties. Second, balancing social development and environmental protection by regard CP as metric for evaluating the environmental health. Finally, allocating medical resources more rationally, especially in northern counties.

The original contributions presented in the study are included in the article/Supplementary material, further inquiries can be directed to the corresponding author/s.

ZH, JJ and XT conceptualized and led the study. XT and ZZ designed the study. Data collection was done by XT and ZZ. XT, ZZ and ZR contributed to data analysis. The first draft of the article was written by XT. ZZ, ZR, HF, and XH reviewed the manuscript and provided critical inputs. All authors contributed to the article and approved the submitted version.

This work was supported by the Provincial Natural Science Foundation of Fujian Province (No. 2021J01728), the Scientific and Innovation Capital Projects of Fujian Province (No. 2022R0088), the Fujian Provincial Health Science and Technology Plan Project (No. 2019-RK-5), and the Fujian Provincial Medical and Health System Reform Research Association Health Policy Innovation Research Project China (No. 2022B07).

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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