Exploring the effects of different types of green exposure on cardiovascular health: Mediated by air pollution, temperature and physical activity

Purpose: The rapid urbanization has led to urban challenges such as traffic congestion, air and noise pollution, and limited public spaces, thereby increasing the risk of residents developing cardiovascular diseases such as hypertension, hyperlipidemia, and heart disease. The impact of green exposure on cardiovascular health has been a focal point of research both domestically and internationally. Studies have shown that urban green spaces can improve residents'' cardiovascular health through various means. For example, they provide mental restoration, alleviate stress, and improve psychological well-being; encourage outdoor exercise among residents; reduce air pollution; and regulate temperatures to mitigate the adverse effects of extreme temperatures on the cardiovascular system. Overall, urban green spaces play an important role in promoting residents'' cardiovascular health. However, there may be variations in the mechanisms through which green exposure promotes cardiovascular health, warranting further exploration of the relationship between green exposure and cardiovascular health. However, the mechanisms through which green exposure promotes cardiovascular health may vary and require further exploration. Firstly, existing research has inadequately addressed the comprehensive effects and pathways of different types of green exposure on cardiovascular health. Most studies have focused on the relationship between single measures of green exposure and cardiovascular health indicators such as air pollution, temperature, or physical activity, such as vegetation coverage or park greenery. Meanwhile, urban streets are gradually becoming important places for residents'' daily communication, leisure, and physical activity. Compared to specific park areas, street green spaces have characteristics such as wider contact range, longer boundaries, and higher accessibility. Secondly, most existing studies have analyzed the relationship between green spaces and health outcomes at the individual micro level within certain buffer zones centered around individual households. However, buffer zone analysis centered around households cannot fully reflect the impact of green spaces on the entire community. In contrast, studies focusing on streets as research units can cover a wider range of people and areas, with large sample sizes and consideration of proximity effects, enabling a more comprehensive reflection of the health status and needs of different populations, which helps formulate more universally applicable health intervention measures. Therefore, this study aims to reveal how different types of green exposure, including vegetation coverage, park accessibility, street greenery, and per capita park area, influence cardiovascular health through potential mediating factors such as air pollution, temperature, and physical activity. Method Taking Shanghai as an example, this study uses Partial Least Squares Structural Equation Modeling (PLS-SEM) to analyze the pathways through which different types of green exposure affect cardiovascular health. By comprehensively considering three potential mediating factors—air pollution (PM2.5 concentration), extreme high temperatures, and levels of physical activity—the study systematically explores the direct and indirect effects of vegetation coverage, park accessibility, street greenery, and per capita park area on cardiovascular disease mortality rates. Data sources include cardiovascular disease mortality data provided by the Shanghai Municipal Center for Disease Control and Prevention, PM2.5 concentration data obtained from MODIS satellite, temperature data obtained from Google Earth Engine, and levels of physical activity calculated based on Location-Based Services data. Results The study found that green exposure not only directly predicts cardiovascular disease mortality rate but also indirectly affects the relationship between green exposure and cardiovascular disease mortality rate through levels of physical activity as a mediator. Street greenery, vegetation coverage, and per capita green space can reduce cardiovascular disease mortality rates by increasing residents'' physical activity levels. It is worth noting that although areas with higher street greenery and vegetation coverage have higher PM2.5 particle concentrations, and areas with larger per capita green space have lower PM2.5 particle concentrations, these factors do not indirectly affect cardiovascular disease mortality rates through PM2.5 particle concentration. Additionally, the study found that building density not only directly predicts cardiovascular disease mortality rate but also indirectly affects the relationship between green exposure and cardiovascular disease mortality rate through levels of physical activity as a mediator. Conclusion This study deeply reveals the complex mechanisms through which different types of green exposure affect cardiovascular health, particularly highlighting the critical mediating role of physical activity. The results indicate that increasing street greenery, vegetation coverage, and per capita park area can promote residents'' physical activity levels, thereby reducing cardiovascular disease mortality rates. Although no significant mediating effect of air pollution was observed, the potential role of green spaces in regulating air quality should not be overlooked. These research findings enrich the theoretical framework of the impact of green exposure on chronic non-communicable diseases and provide important scientific support for urban planning and health promotion policies. In urban planning practice, the configuration of different types of green exposure should be comprehensively considered to fully leverage the benefits of green spaces for cardiovascular health and enhance the overall health levels of urban residents.