EPH PhD Students Research Climate Change and Cardiovascular Health

Annabel Tan

Exposure to poor air quality due to pollution or extreme heat can increase the risk of cardiovascular events like heart attack and stroke, particularly in people already at risk for those conditions. Two Epidemiology and Population Health PhD students are working to improve understanding of the impact of climate change on cardiovascular health. 

Annabel Tan, a 3rd year PhD student with an MPH in epidemiology, has worked as a research professional in the realm of global health, chronic disease and health policy for the past 8 years. 

“I want to understand how a warmer climate will affect cardiovascular health and how health disparities interact with temperature,” she says. “I think it’s really important to understand how a changing climate affects our cardiovascular health. Extremes of temperature are associated overall with increases in cardiovascular mortality.”

Tan is particularly interested in understanding why rising temperatures are impacting some people more than others. She is investigating how ambient temperatures affect blood pressure in the Jackson Heart Study in Jackson, Mississippi, an area with a high burden of cardiovascular disease and health disparities.

“It is important to understand not only how temperature affects cardiovascular health and its risk factors such as blood pressure; it’s also critical to address this issue among African Americans who have been disproportionately burdened with chronic disease. The Jackson Heart Study is the largest study of causes of cardiovascular disease in African Americans. I hope that this work will make a small impact in this area.”

In another project, she is exploring the concept of measured lifespace (the geographic footprint of where people live, work, and recreate) and ambient temperature and how health disparities such as income inequality at a zip code level can affect this association. While most studies examine residential addresses as the primary environment, this study will also include data on where people spend their time. An iPhone app developed in cooperation with the Stanford Biodesign Center creates individual life-space maps using GPS-based methods and will provide data on where people spend their time, allowing researchers to study features of the social and built environments that contribute to or prevent healthy outcomes. Her team will begin collecting data from participants in the REGARDS study this spring and begin analysis in the fall.

Andy Chang

Andy Chang, MD, is a practicing cardiologist working on his PhD in Epidemiology and Population Health Sciences. His clinical experiences have informed his research projects, as his patients have frequently asked him about the implications of climate change-mediated factors like wildfires on their heart health. 

“I’m interested in the impact of environmental forces on the cardiovascular system,” he explains. He is currently examining the association of air pollution exposure with alterations in speckle-tracking echocardiography, a relatively new cardiac imaging technique that allows for the detection of subclinical markers of cardiac functional alterations such as myocardial strain. “This study will contribute to literature on possible tissue-level mechanisms of air pollution-induced cardiac injury,” he says. "It may also serve as an 'early detection system' of sorts before full-blown heart disease develops in affected individuals". 

In a separate project, Chang is working on quantifying the health effects of a particularly severe wildfire event, the 2019 Kincade Fire of Northern California. Serving as health analyst on a multidisciplinary team headed by Stanford professors Dr. Marshall Burke and Dr. Kari Nadeau, he assisted the Sonoma County District Attorney's Office by examining the relationship between wildfire plume exposure and cardiopulmonary emergency room visits. "It was an amazing experience outside of the usual academic system and one that I will always remember".

Finally, Tan and Chang are working together on a project to evaluate the effects of extreme heat events on cardiovascular disease-related emergency department visits in California, a state undergoing frequent anthropogenic environmental disasters such as extreme heat, wildfires and severe drought. This project, led by Tan, uses a large dataset spanning 2013-2020 from the State of California’s Department of Health Care Access and Information and will evaluate whether income level and inequality modify this relationship.

“My big takeaways from doing research in this field is realizing two things: (1) that the heart bears a disproportionate burden of stress from climate change-mediated health hazards, and (2) as one of my career mentors, Dr. Michele Barry, likes to say: you cannot have healthy people without a healthy planet,” says Chang. “The wellbeing of the global population is inextricably (and increasingly) linked to environmental stability.”

Chang recommends visiting the Planetary Health Alliance site to learn more about climate change.