Extreme heat linked to higher all-cause mortality among US adults
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Extreme heat was associated with higher all-cause mortality among adults in the contiguous United States from 2008 to 2017, according to findings published in JAMA Network Open.
Moreover, higher mortality rates were reported for older adults, men and non-Hispanic Black adults.
“Climate change and the impact it has on extreme weather events of many types, including extreme heat, will play an increasingly important role in the health of communities around the world,” Sameed Ahmed M. Khatana, MD, MPH, an assistant professor of medicine at the University of Pennsylvania Perelman School of Medicine and a staff cardiologist at Philadelphia VA Medical Center, told Healio.
“As extreme heat events increase over the coming decades, this will likely become an even greater issue,” he added. “Additionally, as with many other public health issues in the U.S., the adverse health effects appear to fall disproportionately on certain populations. Therefore, efforts to mitigate the effects of extreme heat on the health of vulnerable populations are crucial to prevent these disparities from widening further.”
Khatana and colleagues conducted a longitudinal analysis on the association between extreme hot days in summer months from 2008 to 2017, according to the CDC’s Environmental Public Health Tracking Program, and county-level all-cause mortality rates, according to the National Center for Health Statistics. The analysis included data on 219,495,240 adults aged 20 years and older in 3,108 counties in the lower 48 states of the U.S. Among the study cohort, 51.6% were women and 17.6% were aged older than 65 years.
There was a median of 89 extreme heat days during the summer months of the study period. Khatana and colleagues reported that each additional extreme heat day was associated with 0.07 additional deaths per 100,000 adults (95% CI, 0.03-0.1). Additional analyses revealed that greater increases in mortality rates impacted older adults (0.19 death per 100,000 individuals; 95% CI, 0.04-0.34) compared with younger adults; men (0.12 death per 100,000 individuals; 95% CI, 0.05-0.18) compared with women, and non-Hispanic black adults (0.11 death per 100,000 individuals; 95% CI, 0.02-0.2) compared with non-Hispanic white adults.
Based on the annual population and monthly number of extreme heat days in each county, extreme heat days were associated with an estimated 1,373 additional deaths (95% CI, 584-2,163) per year, on average, the researchers reported. Estimated annual excess deaths varied from 752 (95% CI, 319-1,184) in 2008 to 2,337 (95% CI, 993-3,681) in 2011.
The association between extreme heat and all-cause mortality was significant in metropolitan counties (0.09 death per 100,000 individuals; 95% CI, 0.04-0.13) but not nonmetropolitan counties (0.03 death per 100,000 individuals; 95% CI, 0.03 to 0.09).
The increased risk for mortality may be driven by several individual factors, according to Khatana. For example, people with preexisting conditions like diabetes are particularly vulnerable to the adverse health effects of extreme heat. Also, people taking certain medications like beta-blockers have altered thermoregulation.
“Primary care providers, as the main contact with the health care system for most Americans, are extremely important in both making their patients aware of the adverse health effects of extreme heat and in informing their local, regional and national policy makers of the need to address this important public health issue,” Khatana said. “PCPs can identify individuals, particularly those at high risk for experiencing adverse health effects, those with a high level of medical comorbidities, those who are frail, people living alone, and those who may need access to adequate cooling during extreme heat events.”
Perspective
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Extreme heat exposure is a rising public health concern. In response to rising temperatures, states across the country are expanding their heat illness prevention programs. Some states, such as Arizona, North Carolina and New York, are participating in the CDC Climate Ready Cities and States Initiative to develop these programs. In addition to providing guidance for staying safe in heat, states like New York are incorporating tree planting, white/vegetated roofing and light-colored sidewalks in their work to reduce community temperatures.
Identifying high-risk groups is critical to targeting heat mitigation and illness prevention efforts. By focusing on all-cause mortality, rather than only deaths directly attributable to heat exposure, Khatana and colleagues capture the wider impact of heat on mortality and provide a more accurate depiction of who is at greatest risk.
Consistent with prior research, the study identifies higher risk of heat-associated mortality in older versus younger adults, men versus women and non-Hispanic Black versus non-Hispanic white adults. The authors hypothesize that greater proportion of non-Hispanic Black adults in urban areas, as well as reduced access to high quality health care by underrepresented racial and ethnic groups, may be contributing to the noted disparity in mortality risk.
Research by Jeremy S. Hoffman, PhD, and colleagues identified an association between urban heat exposure and the historical racist housing policy of redlining. Their study of 108 urban areas in the U.S. found that formerly redlined areas were consistently hotter than non-redlined areas, by as much as 7 degrees Celsius. These communities remain predominantly low-moderate income and communities of color. Though banned in 1968, redlining reverberates today in reduced tree cover, more impervious surface and hotter temperatures in affected communities.
Targeting communities with higher proportion of at-risk individuals, as identified by this article and Hoffman’s work, will both protect a high-risk population and help redress historical racist policies such as redlining. This paper provides further justification for investing in the health of these wronged communities today.
Reference:
Hoffman JS, et al. Climate. 2020;doi:10.3390/cli8010012.
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