PUBLICATIONS LIST
*Corresponding author
30. Wang, J., Yang, Y., Peng, J., Yang, L., Gou, Z., & Lu, Y*. (2021). Moderation effect of urban density on changes in physical activity during the coronavirus disease 2019 pandemic. Sustainable cities and society, 72, 103058. (Click for full text of PDF)
Various social distancing measures were carried out in many cities worldwide during the coronavirus disease 2019 pandemic (COVID-19). These measures have led to decreased physical activity levels and higher health risks among urban populations. Strong evidence has been established that built environment characteristics can stimulate physical activity and thus improve public health during non-pandemic periods. Urban density was arguably one of the most important built environment characteristics. However, little is known about whether high urban density amplifies or attenuates the decline in physical activity during the pandemic. Based on two-wave physical activity data collected before and during the pandemic (in January and May 2020, respectively), we used moderation analysis to compare the changes in physical activity levels between people living in low- and high-density neighborhoods. Our results showed that people living in low-density areas have a smaller decrease in physical activity conducted in neighborhood, compared to those living in high-density areas. Our findings suggest that a flexible and porous urban development strategy could enhance the resilience of a city during the coronavirus pandemic and beyond.
29. Lu, Y.*, Zhao, J., Wu, X., & Lo, S. M. (2021). Escaping to nature during a pandemic: A natural experiment in Asian cities during the COVID-19 pandemic with big social media data. Science of the total environment, 777, 146092. (Click for full text of PDF)
As global communities respond to the spread of coronavirus disease 2019 (COVID-19), urban residents worldwide have reduced their mobility, which may have incidentally kept people away from greenspaces. Surprisingly, anecdotal evidence suggests greenspace use surged in Asian cities. In this study, we used the COVID-19 pandemic as a natural experiment to investigate individuals' behavioral changes in greenspace use before and during the pandemic. We created a longitudinal panel dataset comprising Instagram posts from 100,232 users relating to 1185 greenspaces in four Asian cities: Hong Kong, Singapore, Tokyo, and Seoul. We found a 5.3% increase in the odds of people using greenspaces for every 100-case increase in weekly new cases. The models also revealed that people prefer nature parks that are large and close to city centers. In summary, because of the established physical and mental health benefits of greenspaces, people have been escaping to nature to cope with the pandemic in Asian cities.
28. Lu, Y., Chen, L., Liu, X., Yang, Y., Sullivan, W. C., Xu, W., Webster, C. & Jiang, B*. (2021). Green spaces mitigate racial disparity of health: A higher ratio of green spaces indicates a lower racial disparity in SARS-CoV-2 infection rates in the USA. Environment international, 152, 106465. (Click for full text of PDF)
There is striking racial disparity in the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection rates in the United States. We hypothesize that the disparity is significantly smaller in areas with a higher ratio of green spaces. County level data on the SARS-CoV-2 infection rates of black and white individuals in 135 of the most urbanized counties across the United States were collected. The total population in these counties is 132,350,027, comprising 40.3% of the U.S. population. The ratio of green spaces by land-cover type in each county was extracted from satellite imagery. A hierarchical regression analysis measured cross-sectional associations between racial disparity in infection rates and green spaces, after controlling for socioeconomic, demographic, pre-existing chronic disease, and built-up area factors. We found a higher ratio of green spaces at the county level is significantly associated with a lower racial disparity in infection rates. Four types of green space have significant negative associations with the racial disparity in SARS-CoV-2 infection rates. A theoretical model with five core mechanisms and one circumstantial mechanism is presented to interpret the findings.
27. Jiang, B., Shen, K., Sullivan, W. C., Yang, Y., Liu, X., & Lu, Y.* (2021). A natural experiment reveals impacts of built environment on suicide rate: Developing an environmental theory of suicide. Science of the total environment, 776, 145750. (Click for full text of PDF)
Background
Suicide is a global challenge. Although it is clear that socioeconomic and demographic factors influence suicide rates, we know little about the impacts of the built environment on suicide rates.
Methods
We investigated the relationship between characteristics of the built environment and suicide death rates over a 13-year period in 151 rent-only public housing communities in Hong Kong. The regulations of the public housing authority in Hong Kong constituted a natural experiment with minimal self-selection bias. We conducted hierarchical regression analyses and found that characteristics of the built environment were significantly associated with suicide rates after controlling for SES and demographic factors at the community level.
Results
Three significant environmental factors were identified distance to the nearest urban center, distance to the nearest Mass Transit Railway station, and gross flat area per person.
Conclusion
These findings demonstrate a significant association between features of the built environment and suicide rates. They also suggest possible interventions that might reduce suicide through design, or redesign, of the built environment. Lastly, we propose an environmental theory of suicide based on the Interpersonal Theory of Suicide.
26. Yang, Y., Lu, Y.*, Yang, L., Gou, Z., & Liu, Y. (2021). Urban greenery cushions the decrease in leisure-time physical activity during the COVID-19 pandemic: A natural experimental study. Urban forestry & urban greening, 62, 127136. (Click for full text of PDF)
The coronavirus disease 2019 (COVID-19) pandemic and related social distancing measures have altered the daily lifestyles of people worldwide. Although studies on this disease are emerging rapidly, less is known about the impacts of COVID-19 and urban greenery on leisure-time physical activity, which is critical to maintain health for urban residents during the pandemic. In this study, we used a natural experimental research design to identify whether urban greenery cushions the decrease in leisure-time physical activity caused by the pandemic and related social distancing measures in a high-density city. The two-wave physical activity data (before and during the pandemic) were collected for urban residents in neighborhoods with high or low levels of greenery. The results of difference-in-differences model suggest that urban greenery mitigated the decrease in physical activity during the pandemic. People who lived in greener neighborhoods experienced a lesser decrease in the leisure-time physical activity level than those who lived in less green neighborhoods. Additionally, people who lived in greener neighborhoods experienced increased levels of physical activity related to visits to country parks during the pandemic. These findings suggest that urban green spaces play a significant role in shaping physical activity and providing a refuge for the public during crises. Our study is among the first to investigate the impact of urban greenery on pandemic-induced changes in leisure-time physical activity in densely populated Asian cities, and our findings shed light on the potential protective role of urban greenery on public health during the COVID-19 pandemic and beyond.
25. Yang, H., He, D.*, Lu, Y.*, Ren, C., & Huang, X. (2021). Disentangling residential self-selection from the influence of built environment characteristics on adiposity outcomes among undergraduate students in China. Cities, 113, 103165. (Click for full text of PDF)
Although many studies have confirmed the effects of the built environment on adiposity outcomes in the general population, evidence for young adults is scarce. Furthermore, most prior studies are prone to residential self-selection bias due to the nature of cross-sectional research design, which makes the built environment–adiposity relationship spurious. In this study, we explored the associations between the built environment and three objectively measured adiposity outcomes for a large representative sample of 20,227 undergraduate students from 89 university campuses in China. The adiposity outcomes were measured by body mass index (BMI), waist circumstance (WC), and waist-to-height ratio (WHtR). The residential self-selection bias was largely mitigated because these students are required to live in campus dormitories. As shown by multilevel models, street connectivity, population density, and Normalized Difference Vegetation Index (NDVI) within and around the campus environment were negatively associated with the odds of adiposity to different extents. Furthermore, the adiposity outcomes of male and low cost-of-living undergraduates were more likely to be affected by built environment characteristics compared to female and high cost-of-living undergraduates. Hence, to deliver effective environment interventions to curb the prevalence of adiposity among undergraduate students, policymakers and university managers are advised to create a more carefully conceived campus environment.
24. Yang, Y., Lu, Y.*, Yang, H., Yang, L., & Gou, Z. (2021). Impact of the quality and quantity of eye-level greenery on park usage. Urban forestry & urban greening, 60, 127061. (Click for full text of PDF)
Urban parks have well-documented health benefits for urban residents. To increase the use of parks and enhance the physical activity level of city-dwellers, recent studies have explored the link between the amount of greenery in parks and the level of park usage. However, the results have been inconsistent, partly due to different measurements of park greenery. In this study, we developed a novel method to assess both the quantity and quality of park greenery from eye-level photographs taken along major paths in parks. The quantity of greenery in these photographs was objectively assessed with advanced machine learning techniques (PSPNet), and the quality of greenery was assessed by virtual audit. The associations between greenery and usage of 43 urban parks were further explored with regression models. The results showed that the quality of greenery has stronger association with total number of park visitors than the quantity. Both the quantity and quality of greenery had stronger associations with the number of elderly visitors (apparent aged 65 or above) than with the numbers of children or adults. Our results bring new insights into how park greenery can encourage park usage and contribute to healthy cities.
23. Wang, J., Wu, X., Wang, R., He, D., Li, D., Yang, L., Yang, Y. & Lu, Y.* (2021). Review of associations between built environment characteristics and severe acute respiratory syndrome coronavirus 2 infection risk. International Journal of Environmental Research and Public Health, 18(14), 7561. (Click for full text of PDF)
The coronavirus disease 2019 pandemic has stimulated intensive research interest in its transmission pathways and infection factors, e.g., socioeconomic and demographic characteristics, climatology, baseline health conditions or pre-existing diseases, and government policies. Meanwhile, some empirical studies suggested that built environment attributes may be associated with the transmission mechanism and infection risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, no review has been conducted to explore the effect of built environment characteristics on the infection risk. This research gap prevents government officials and urban planners from creating effective urban design guidelines to contain SARS-CoV-2 infections and face future pandemic challenges. This review summarizes evidence from 25 empirical studies and provides an overview of the effect of built environment on SARS-CoV-2 infection risk. Virus infection risk was positively associated with the density of commercial facilities, roads, and schools and with public transit accessibility, whereas it was negatively associated with the availability of green spaces. This review recommends several directions for future studies, namely using longitudinal research design and individual-level data, considering multilevel factors and extending to diversified geographic areas.
22. Xie, B., Lu, Y.*, Wu, L., & An, Z. (2021). Dose-response effect of a large-scale greenway intervention on physical activities: The first natural experimental study in China. Health & Place, 67, 102502. (Click for full text of PDF)
Although many cross-sectional studies have confirmed the positive associations between greenspaces and physical activity, evidence from natural experiments is scarce, especially for large-scale greenspace interventions. In addition, it is unclear how the physical-activity-related benefits of a greenspace intervention vary with distance from residences to greenspaces. We used a natural experimental approach to explore the impact on physical activity of a large-scale greenway intervention, namely the East Lake greenway, in Wuhan, China. Two waves of survey data (before and after the intervention in 2016 and 2019, respectively) were collected from 1020 participants residing in 52 neighbourhoods at different distances (0–1, 1–2, 2–3, 3–4, and 4–5 km) from the 102-km-long greenway. The results obtained using difference-in-difference models indicated that the greenway intervention had positive effects on both moderate-to-vigorous physical activity (MVPA) and overall physical activity (MET-minutes/week) after controlling for individual and neighbourhood covariates. Furthermore, the physical activity benefits of the greenway intervention were found to decrease with increasing distance between the greenway and the participants’ residences. Individuals living closer to this large-scale greenway accrued more substantial physical activity benefits. Our results, together with those of other natural experimental studies, suggest that large-scale greenspace interventions may provide long-term physical activity benefits to residents living in a wide geographic area.
21. He, H., Lin, X., Yang, Y., & Lu, Y.* (2020). Association of street greenery and physical activity in older adults: A novel study using pedestrian-centered photographs. Urban Forestry & Urban Greening, 55, 126789. (Click for full text of PDF)
Urban parks and tree-lined streets are major components of urban greenspaces, as well as the most frequently used public spaces for senior citizens. Studies have shown significant associations between urban greenspaces and various health outcomes of older adults. However, most of them focused on urban parks or overall vegetation coverage, and few have considered the impact of street greenery. The lack of research attention on the latter is partly because of no method objectively measuring greenery exposure on streets, especially from a pedestrian-centered perspective. In the current study, we recruited 1161 adults aged 60 or above who lived in 12 housing estates in Wuhan, China, and collected their socio-demographic data and 7-day physical activity data. Streetscape photos were taken by trained researchers on sidewalks of all streets in the 800-m buffers from these housing estates. The pedestrian-centered street greenery exposure was extracted from these photos with the machine learning technique of convolutional neural networks along with the pyramid pooling module. Multilevel logistic regression models were conducted to examine the association of the frequency (≥4 days vs. < 4 days) and total duration (≥300 mins vs. <300 mins) of physical activity with street greenery. Park area, population density, street connectivity, and land use mix within the buffer zone, as well as individual factors, were included as covariates in the models. Results showed that street greenery was positively associated with the odds of achieving 300 mins or more of physical activity per week, but the park area was not. Furthermore, street connectivity and land use mix were positively associated with both the frequency and total time of physical activity. Unexpectedly, population density was negatively associated with the frequency and total time of physical activity. Therefore, adding street greenery or improving existing street greenery can be a vital environment-intervention strategy to create an aging-friendly urban environment.