Article Text

Download PDFPDF
Effects of social vulnerability and heat index on emergency medical service incidents in San Antonio, Texas, in 2018
  1. Lisa K Zottarelli1,
  2. Hatim O Sharif2,
  3. Xiaohe Xu3,4,
  4. Thankam S Sunil5,6
  1. 1 College of Social Work and College of Education, Health, and Human Sciences, University of Tennessee, Knoxville, Tennessee, USA
  2. 2 Department of Civil and Environmental Engineering, University of Texas at San Antonio, San Antonio, Texas, USA
  3. 3 Sociology, University of Texas at San Antonio, San Antonio, Texas, USA
  4. 4 School of Public Administration, Sichuan University, Chengdu, China
  5. 5 Public Health, University of Tennessee, Knoxville, Knoxville, TN, USA
  6. 6 West China School of Public Health, Sichuan University, Chengdu, China
  1. Correspondence to Lisa K Zottarelli College of Social Work and College of Education, Health, and Human Sciences University of Tennessee, Knoxville, TN, USA; LZottare{at}


Background Excessive heat is a leading weather-related cause of fatalities in the USA. Vulnerable populations can face greater exposure to health risks during extreme heat events. The aim of this study is to examine the effects of excessive heat and community-level social vulnerability on morbidity in San Antonio, Texas, in 2018.

Methods Heat Index (HI) data are from the National Oceanic and Atmospheric Administration. Social vulnerability is measured using the Centres for Disease Control and Prevention’s Social Vulnerability Index (SVI). Morbidity is measured as the number of emergency medical service (EMS) incidents. Sixty-one zip codes were analysed for the 153 constrained calendar days from 1 May to 30 September 2018. Negative binomial regression analysis with the time-stratified case-crossover design was conducted to predict the effects of HI and SVI on the rate of EMS incidents.

Results HI is significantly and positively associated with the rate of EMS incidents. Social vulnerability has a statistically significant association with EMS incidents, with higher levels of community-level social vulnerability associated with higher rates of EMS incidents. The effect of the HI on the rate of EMS incidents is significantly and positively moderated by the SVI.

Conclusions Social vulnerability and excessive heat increase the rate of EMS incidents. As the number of excessive heat days increases and San Antonio continues to have extreme disparities by location, there will be an effect on health systems, including EMSs.

  • Morbidity
  • temperature
  • social inequalities
  • environmental health

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.


  • Contributors LKZ and HS conceived the research question. LKZ designed the study, extracted and managed the data, and wrote the first and subsequent drafts of the manuscript. TS contributed to data management and study design. XX conducted the analysis and wrote the Results section. All authors contributed advice and comments on the results and revision of the manuscript. All authors approved the final draft.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Ethics approval The George Washington University Institutional Review Board determined that the project does not meet the regulatory definition of human subjects research in U.S. federal regulations at 45 C.F.R. 46.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement SVI and HI data are publically available. EMS data may be obtained from a third party and are not publically available.