The Increasing Death Toll in the U.S. From Extreme Heat

Last summer, in the Pacific Northwest, record temperatures melted power cables and buckled roads. Seattle reached a record high of 108 degrees and millions of area residents struggled under the weight of unprecedented heat. Just this year, New York and Boston experienced their earliest heat advisories on record and heat waves are again hitting the U.S. I am a cardiologist – you might wonder why am I so concerned about heat?

During the heat wave last summer in the Northwest, approximately 600 additional people died over a week in Oregon and Washington. As climate increases the frequency of extreme weather events like heat waves, my patients and many others will face severe health consequences. According to estimates by the National Weather service, heat has been the single largest contributor to weather related deaths over the last 30 years.

In two recent studies, my colleagues and I investigated the number of deaths linked to extreme heat events in the contiguous U.S. We found that between 2008 and 2017 between 13,000 to 20,000 adult deaths were linked to extreme heat, with approximately half of them due to heart disease. Another recent study which examined hot weather, rather than extreme heat, suggested that up to 20,000 deaths a year in North America may be linked to hot temperatures.

The human body functions in a narrow temperature window and multiple mechanisms in the body attempt to keep it within that optimal window. Extreme heat stresses every organ in the human body as it struggles to control its core temperature. The heart plays a crucial role in this, as it helps pump blood away from the central parts of the body to the skin. For people with pre-existing heart disease or conditions like high blood pressure and diabetes, the extra strain placed on the heart by extreme heat can lead to heart attacks and strokes. Finally, if heat levels continue to increase, the body suffers from multi-organ failure and eventually death.

Like all public health issues in this country, the burden of extreme heat falls unequally on certain people. Our study found that the link between extreme heat and deaths was stronger in older compared to younger adults, men compared to women, and Black compared to white adults. Heart disease, diabetes and other chronic medical conditions can make a person more vulnerable to the health effects of extreme heat. Since on average, older individuals, men, and Black Americans are more likely have these conditions, they may suffer the health consequences of extreme heat to a greater degree.

However, there are other, structural reasons behind some of these differences. Due to the long history of segregation and discriminatory housing practices in the U.S., Black Americans tend to live in neighborhoods that are uniquely vulnerable to extreme heat. In New York, buildings in minority neighborhoods are hotter and more humid than those in white neighborhoods. Tree cover, an important defense against the sun, is lower in minority neighborhoods, and Black Americans are less likely to have access to air conditioning. The injustice of this disparity is highlighted even more by the fact that CO2 emissions from white households are significantly higher than from Black households.

As a physician, I can provide my patients with health care that will increase their odds of surviving extreme heat events, but that can only do so much. Although Federal efforts for comprehensive plans to tackle climate change are stalled in Congress, there is some momentum to understand the health impact of climate change, including extreme heat. In January 2021 the Department of Health and Human Services established the Office of Climate Change and Health Equity to serve as a department-wide hub for climate change and health policy. In May, OCCHE began issuing its Climate and Health Outlook and the June issue includes resources for extreme heat events.

These measures are a welcome start, but they are far from enough. We need urgent interventions to make neighborhoods more resilient to extreme heat. In the absence of any national plan to address the impact of extreme heat, there is a patchwork of state and local regulations with varying levels of protections and resources for Americans. Currently 33 states have no protections against power shutoffs during extreme heat events. The establishment of cooling centers is similarly haphazard. A survey of New York State counties found that more than one third had no clear cooling plan and had no plans to establish cooling centers. Cooling centers, once established, need to be readily accessible to vulnerable individuals who unable to access air conditioning at home, and regulations preventing power disconnection during periods of extreme heat should be enacted. Beyond ensuring access to cooling, whether at home or in cooling centers, urban greening and increasing tree cover can also play an important role in lessening the effects of extreme heat on a neighborhood. In the longer term, our policy makers and industry leaders should heed the warning signs provided by these deaths and understand the urgency of cutting greenhouse gas emissions. By the middle of this century, most parts of the country are likely to experience 20 to 30 more extreme heat days a year. If infrastructure to mitigate the health effects of heat is not developed, more people are likely to die each year.