Study: Heat-related mortality is a problem across Washington state

Study: Heat-related mortality is a problem across Washington state

Heat-related deaths are a problem across Washington state and occur even in regions with typically milder climates, according to a University of Washington study published Aug. 30 in the journal Atmosphere. This is the largest study of heat-related mortality in Washington state to date and the first to expand beyond major population centers to include rural areas.

Nationally, in recent decades, the probability of death has been on average 8% higher on days when the combination of temperature and humidity, known as humidex, was in the top 1% of recorded values ​​for that location, compared to a day with a mid-range value for humidex.

"This study shows that heat-related mortality, even in a temperate zone like Washington state, is a current environmental public health concern," said lead author Logan Arnold, who conducted the work as a UW master's student in quantitative ecology and resource management. "It's not a future public health problem that will exist in a warming climate - it's something we're already experiencing now."

Although heat stroke is sometimes listed as the official cause of death, other heat-aggravated illnesses are often the focus. Researchers used statistical methods to uncover “hidden” deaths where something else, such as an illness or chronic illness, may have been reported as the primary cause.

This research adds to existing evidence that the burden of heat effects on health lies in its impact on underlying health conditions. For example, we see an increase in diabetic and cardiovascular mortality associated with extreme hot days. Physiologically, it is more difficult for people with underlying medical conditions to regulate temperature, but it is also likely that medications play a role in the body's ability to dissipate heat.

Tania Busch Isaksen, senior author, associate teaching professor of environmental and occupational health at UW and co-director of the UW Collaborative on Resilience to Extreme Events

The study analyzed deaths recorded by the Washington State Department of Health from 1980 to 2018. The authors only considered non-traumatic deaths from May to September and divided them into ten federally defined climate zones. Heat exposure on the day of death was determined based on the home address and Humidex on that day.

The results confirm what previous studies in King County have shown: Heat actually leads to more deaths, even in places with milder climates.

Mortality rates on Humidex days in the top 1% of historical values ​​were significantly higher in four climate zones: the Puget Sound lowlands, which includes Seattle and other major cities; the eastern slope of the Cascades, which circles Puget Sound but lies further inland; Northeast, which borders Canada and Idaho and includes the city of Spokane; and northeastern Olympic San Juan, which includes all of the San Juan Islands, Port Townsend and a coastal section of the Olympic Peninsula.

Although the total number of deaths in the Northeast Olympic San Juans zone was lower than in the other three regions, this region saw a particularly large increase as humidex increased.

"Location is really important. You can't just apply what we've seen in other parts of the United States to what's happening here," Busch Isaksen said. “This is why local research is crucial to understanding environmental risks.”

In the other climates there was not necessarily a lack of risk, but there was not enough mortality data to determine a statistically certain trend.

The large increase in mortality in places with more temperate climates, according to the authors, could be due to these areas being less prepared for heat, meaning they are less physically adapted to heat and exhibit fewer protective behaviors; or have less adaptable infrastructure such as air conditioning or access to cooling centers.

The study took place before the Pacific Northwest's record-breaking heat wave in 2021. But in addition to looking at historical data, the authors also considered projections for future climate zones in 2030, 2050 and 2080. Three zones (all previous zones except the Northeast) had statistically significant increases in heat mortality. On average across these three regions, heat-related deaths were about a third higher in 2030, more than twice as high in 2050, and six times higher under forecast conditions for 2080.

Although the study did not consider preparedness measures, the results could inform planning efforts across the state.

“If you don't know that your region is experiencing extreme heat — and if you think it's just an Arizona or Texas problem — then you're not prepared,” Busch Isaksen said. “The value of this study is that it provides local environmental organizations with risk information specific to vulnerable populations in their region so they can use their limited resources to develop strategies to reduce heat exposure before the next extreme heat event occurs.”

Another co-author is Mark Scheuerell, associate professor of aquatic and fisheries sciences at the UW. Arnold is now a data analyst at West Virginia University studying ways to improve children's access to mental health services.

Source:

University of Washington

Reference:

Arnold, L., et al. (2022) Mortality Associated with Extreme Heat in Washington State: The Historical and Projected Public Health Burden. Atmosphere. doi.org/10.3390/atmos13091392.