More visible greenspace, stronger heart? Evidence from ischaemic heart disease emergency department visits by middle-aged and older adults in Hubei, China

https://doi.org/10.1016/j.landurbplan.2022.104444Get rights and content

Highlights

  • The association between visible greenspace and ischemic heart diseases (IHD) is still unclear.

  • This study explores the association between residential street view greenspace (SVG) exposure and IHD emergency department visits for middle-aged and older adults.

  • SVG-grass is negatively associated with IHD mortality and recovery time from IHD.

  • No evidence can support SVG-tree is related to IHD.

  • Male patients, older patients and patients living in low-income neighbourhood can benefits more from SVG exposure.

Abstract

Awareness is increasing that greenspace is beneficial for people’s heart health. While a plethora of studies have focused on the relationship between neighbourhood greenspace and cardiovascular diseases in the general population, scant attention has been given to ischaemic heart disease (IHD) emergency department visits for middle-aged and older adults. This study aimed to systematically explore the association between residential street view greenspace (SVG) exposure and IHD emergency department visits for middle-aged and older adults in Chinese cities. The IHD mortality and recovery time of surviving patients were treated as dependent variables. We used street view data to assess residential SVG, and we also distinguished between trees (SVG-tree) and grasses (SVG-grass) when calculating SVG. The results showed that SVG-grass is negatively associated with IHD mortality and recovery time from IHD. However, there is no evidence that SVG-tree is related to IHD. Hence, the stratified analysis indicates that that the effect of SVG on IHD varies significantly by individual demographic and socioeconomic characteristics. Male patients, older patients and patients living in low-income neighbourhoods can benefit more from SVG exposure. Our findings suggest the necessity of providing sufficient residential visible vegetation, especially grassland, to promote heart health in Chinese urban settings.

Introduction

Cardiovascular diseases (CVDs) have become a serious global public health issue (Lozano, et al., 2012). Among all CVDs, ischaemic heart diseases (IHDs) are the leading cause of death globally (Roth, et al., 2017). In China, ischaemic heart disease was also the leading cause of CVD deaths in 2016 (Liu, et al., 2019). Most previous studies have focused on the effect of lifestyle-related behaviours such as drinking and smoking on CVDs (Cosselman et al., 2015, Yang et al., 2015). In recent years, other studies have shown that residential environments, such as greenspace exposure, also contribute to the risk of CVDs.

There are a number of mechanisms underlying the association between greenspace and CVDs (Nieuwenhuijsen, 2018). First, greenspace can mitigate environmental hazards such as air pollution (Aerts, et al., 2020), noise (Nieuwenhuijsen, 2018) and heat waves (Shen and Lung, 2016), which all have negative impacts on CVDs. For example, Aerts et al. (2020) found that air pollution mediates the association between forest cover and cardiovascular medication sales. Shen and Lung et al. (2016) pointed out that green structures reduce the mortality of cardiovascular diseases by mitigating the negative impact of high temperature. Second, restorative features of greenspace help people reduce stress, which is beneficial to CVDs (Nieuwenhuijsen, 2018). A recent study in Australia found that greenspace can improve sleep duration, which helps people restore energy (Astell-Burt and Feng, 2020a). Additionally, Grahn and Stigsdotter (2010) found that urban greenspace is an important restorative environment for stressed individuals.

Finally, greenspace can encourage more physical activity, which enhances physical functions and is beneficial to heart health (Jia et al., 2018, Nieuwenhuijsen, 2018, Richardson et al., 2013, Sharifi et al., 2021, Wu and Kim, 2021, Xie et al., 2018, Yang et al., 2019). Richardson et al. (2013) found that physical activity partly explained greenspace-CVD associations in New Zealand. Jia et al. (2018) also found that physical exercise mediates the effects of greenspace on CVDs in China. Hence, greenspace strengthens social interaction and coherence, which can enhance people’s health-related knowledge and reduce CVDs (Nieuwenhuijsen, 2018). Although the mediating effect of social cohesion has not yet been confirmed, greenspace-social cohesion (Jennings & Bamkole, 2019) and social cohesion-CVD associations (Robinette et al., 2018) have been verified.

Accumulated findings suggest that exposure to greenspace within people's residential neighbourhood is beneficial for heart health (Nieuwenhuijsen, 2018). A recent meta-analysis found that greenspace exposure is significantly related to a reduction in the risk of cardiovascular disease mortality (Gascon, et al., 2016). Various cross-sectional and longitudinal studies have confirmed that exposure to residential greenspace is associated with CVDs (Nieuwenhuijsen, 2018). In a cross-sectional study, Yeager et al. (2018) found that neighbourhood greenspace is associated with a lower risk of CVDs in the USA. Similar results were found in Israel (Yitshak-Sade et al., 2017), Australia (Pereira, et al., 2012), Canada (Chum and O’Campo, 2015) and China (Yang, et al., 2020). However, based on an ecological study design, Richardson et al. (2010) found no evidence that greenspace influenced CVDs in New Zealand.

For longitudinal studies, Seo et al. (2019) found that greater greenspace coverage is associated with a reduced risk of CVD in Korea. Astell-Burt and Feng (2020b) found that tree canopy is negatively associated with the odds of prevalent CVDs in Australia. Chen et al. (2020) observed that residential greenspace is related to CVD incidence, readmission, and mortality in Canada. A field experiment further investigated the health benefits of visiting green environments and found that they are beneficial for blood pressure, heart rate and heart rate variability (Lanki, et al., 2017).

However, most of the existing literature mainly focused on greenspace-chronic CVD associations for the general population, while scant attention has been given to CVD emergency department visits, especially for middle-aged and older adults. Middle-aged and older adults have a higher risk of CVD prevalence and mortality than young adults (Roth, et al., 2017), so further examination of greenspace-CVD emergency department visits, especially for middle-aged and older adults, has become an urgent issue.

The heterogeneous health benefits of greenspaces should also be noted. The ‘equigenesis’ theory indicates that disadvantaged groups can benefit more from greenspace exposure since they may not be able to afford good medical care, and green infrastructure is a kind of public facility that is free to access (Mitchell et al., 2015). For example, Mitchell and Popham (2008) found that the association between greenspace exposure and CVD mortality is stronger for income-deprived groups than for high-income groups. Additionally, gender differences is another aspect of the heterogeneous health benefits of greenspace. For instance, Richardson and Mitchell (2010) found that greenspace exposure is associated with lower CVD mortality for men, but such an association was not significant for women. However, few studies have focused on the heterogeneous health benefits of greenspace in developing countries, so such heterogeneity for greenspace-CVD associations remains unclear in developing countries.

Awareness is increasing that streets have become an important context for greenspace exposure, since people spend a large amount of time in such a context (Chaix et al., 2013, Jiang et al., 2020, Lachowycz et al., 2012, Li et al., 2018, Mennis et al., 2018). For example, Zhang et al. (2020) used wearable cameras to measure people’s dynamic greenspace exposure and found that the proportion of dynamic exposure (which happens on the street) is much greater than that of static exposure. Nieuwenhuijsen (2018) also highlighted that street greenspace is important for CVDs since it is an essential context for walking, cycling and other physical activities. Previous investigations have mainly focused on the impact of greenspace exposure on health based on remote sensing and land use data, with less evidence derived from street-level visible greenspace (Helbich et al., 2021, Markevych et al., 2017). No studies have examined the effect of street-level visible greenspace on CVDs, so it is unclear whether street-level visible greenspace contributes to CVDs. Hence, Astell-Burt and Feng (2020b) found that the tree canopy is associated with CVDs, while total green space is not, so identifying whether different types of street vegetation influence CVDs differently is also necessary.

This study aimed to explore the association between residential street view greenspace (SVG) exposure and IHD for middle-aged and older adults in Hubei, China, using hospital emergency department visits and Tencent street view data. It particularly focuses on the effects of both street-level visible trees and grasses. Additionally, the heterogeneous effects of demographic and socioeconomic status (SES) factors are included. This study extends previous research in several respects. First, it enhances our knowledge of the beneficial effect of residential greenspace exposure on IHD by focusing on middle-aged and older patients in China. Second, it makes a methodological contribution to the study of the cardiovascular benefits of residential greenspace exposure by using street view greenspace as a surrogate for visible greenspace exposure. Last, this study further contributes to the ‘equigenesis’ theory by examining the greenspace-IHD association.

Section snippets

Health outcomes

IHD emergency department visits for 2016–2019 were obtained from Hubei Provincial People's Hospital. IHD identification was based on the primary discharge diagnosis code of each patient. The following outcomes [International Classification of Diseases, Tenth Revision (ICD-10 codes)] were included: acute myocardial infarction [I21], subsequent ST elevation (STEMI) and non-ST elevation (NSTEMI) myocardial infarction [I22], certain current complications following ST elevation (STEMI) and non-ST

Results

Table 2, Table 3 show the results of Model 1. Model 1a indicated that respondents living in neighbourhoods with Q4 SVG grass (OR = 0.701, 95% CI: 0.472–0.942) were less likely to die of IHD. However, there is no evidence that that SVG-tree is associated with IHD mortality. Model 1b indicated that respondents living in neighbourhoods with Q4 SVG grass (Coef. = −0.639, SE = 0.319) had a shorter recovery time from IHD. However, no evidence supports that SVG-tree is associated with the recovery

Discussion

This study extends previous studies on the association between greenspace exposure and IHD in several respects. First, the present study is the first to systematically explore the effect of residential greenspace and IHD for middle-aged and older patients in the Chinese context. Second, it makes a novel methodological contribution to the study of the cardiovascular benefits of residential greenspace exposure in China by focusing on street view greenspace. Third, it further investigates the

Conclusion

This study is the first to systematically explore the association between SVG exposure and IHD emergency department visits for middle-aged and older adults in Chinese cities. The results of the statistical analyses show that SVG-grass is negatively associated with IHD mortality and recovery time from IHD. However, there is no evidence that SVG-tree is related to IHD. Our results pass a series of robustness checks. Hence, the stratified analysis indicates that the effect of SVG on IHD varies

Funding

This work was supported by the National Natural Science Foundation of China (41801306) and the “CUG Scholar” Scientific Research Funds at China University of Geosciences (Wuhan) (Project No. 2022034).

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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