Dr. Ying Li Publishes on Climate Change

Dr. Ying Li, Assistant Professor in East Tennessee State University College of Public Health’s Department of Environmental Health, is lead author of an article titled “Heatwave Events and Mortality Outcomes in Memphis, Tennessee: Testing Effect Modification by Socioeconomic Status and Urbanicity” in the International Journal of Environmental Research and Public Health. The article is part of the special issue Climate change and Public Health: Emerging Knowledge on Impacts and Vulnerabilities.

Dr. Andrew Joyner of ETSU’s Department Geosciences is a co-author along with researchers from the University of Memphis, the Children’s Foundation Research Institute, and the Shelby County Health Department.

The overall rising temperature in the 21st century resulting from climate change is likely to be the most serious global health threat of the century. Heatwaves are natural hazards that pose significant risks to human health.  Heatwave studies typically estimate heat-related mortality and morbidity risks at the city level; few have addressed the heterogeneous risks by socioeconomic status and location within a city. 

This study aimed to examine the impacts of heatwaves on mortality outcomes in Memphis, Tennessee and the surrounding Shelby County.  The average high temperature in July and August is approximately 92 °F, and relative humidity is commonly greater than 65%. Heat indexes frequently exceed 100 in summer, and the National Weather Service-Memphis office often issues heatwave warnings and advisories in the area.

The researchers analyzed the association between heatwaves and daily mortality among elderly aged 65 years and above in Shelby County, Tennessee in 2008–2017, and investigated the effects of socioeconomic status and urbanicity level on heatwave-related mortality risks based on two statistical models, four distinct heatwave definitions, and three categories of mortality outcomes. They found a slight increase of all-cause mortality due to heatwave events, and this was mostly driven by an approximately 25% increase of cardiovascular mortality based on a particular heatwave definition.

They did not find significant interaction effects between heatwave effects and sociodemographic parameters or air pollution. The findings suggested that the cardiovascular mortality risk due to heatwave events remained nontrivial in the South region of the U.S., despite the high availability of air conditioning and population acclimatization, contributing to the relatively lower vulnerability to heat-related mortality. Future research is needed to extend the analysis to a longer period, validate the generalizability of the findings in other large urban areas, and improve heat exposure assessment at the community and individual levels.