Extreme heat linked to rise in US death rates: study

Extreme heat events, on the rise due to climate change, are associated with higher overall adult death rates across the U.S., a new study has found.

From 2008 through 2017, each additional extreme heat day per month was linked to 0.07 additional deaths per 100,000 adults — or 7 deaths per 10 million adults — during the same period, according to the study, published in the Journal of the American Medical Association on Thursday.

“Our study demonstrates that extreme heat is already associated with a higher mortality rate across the contiguous United States,” lead author Sameed Khatana, an assistant professor at the University of Pennsylvania’s Perelman School of Medicine, told The Hill.

“As extreme heat events increase over the coming decades, this will likely become an even greater issue,” Khatana added.

While the scientists determined that extreme heat contributed to increased death rates across the U.S. in general, they pinpointed even greater increases among older adults, men and non-Hispanic Black individuals.

Without mitigation, the authors warned, the expected increase in extreme heat due to climate change could exacerbate existing health gaps among these groups.

“As with many other public health issues in the United States, the adverse health effects appear to fall disproportionately on certain populations, notably on non-Hispanic Black adults,” Khatana said.

“Therefore, efforts to mitigate the effects of extreme heat on the health of vulnerable populations is crucial to prevent these disparities from widening further,” he added.

To draw their conclusions, the scientists cross-checked the number of extreme heat days in the summer months from 2008 to 2017 and county-level “all-cause mortality rates” across all counties in the contiguous U.S. The death figures, obtained from the National Center for Health Statistics, included adults aged 20 years and older, according to the study.

Of the total 219.5 million adults residing in the contiguous U.S. in 2008, about 113 million were women and 38.5 million were older than 65 years, the authors noted.

From 2008 to 2017, the median number of extreme heat days during summer months in all 3,108 counties surveyed was 89 days, according to the study.

The scientists found greater increases in mortality rates in older adults (0.19 death per 100,000 individuals) and for males (0.12 death per 100,000 individuals). They also observed bigger increases in non-Hispanic Black individuals (0.11 death per 100,000 individuals).

While the authors acknowledged that the association between extreme heat and adverse health outcomes has been studied previously, they stressed that most research has been limited to certain parts of the U.S. and predominantly to urban areas — making the total burden of excess deaths unclear.

Because the connection between extreme heat and health outcomes is influenced by elements of the built environment — like tree cover and air conditioning — investigating that burden needs to occur over a broader portion of the country, the scientists said.

With that in mind, the authors also noted that vulnerable and historically oppressed communities often endure disproportionate impacts of extreme heat due to differences in health care access, residence in areas with greater risk of extreme heat exposure and the burden of other illnesses.

Pinpointing which communities face such disproportionate effects could allow investors to ensure that funding mechanisms “guard against the adverse health outcomes associated with extreme heat,” according to the authors.

“Local, regional and national policy makers need to make mitigating the health effects of climate change in general, and extreme heat in particular, a priority,” Khatana told The Hill.

“For extreme heat, making neighborhoods — particularly those in which vulnerable populations live — more resilient to the effects of extreme heat, such as through increasing tree cover and ensuring access to cooling centers, may play a role,” he added.