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Hidden Toll of the Northwest Heat Wave: Hundreds of Extra DeathsSkip to Comments
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Hidden Toll of the Northwest Heat Wave: Hundreds of Extra Deaths

Week of the

heat wave

+400

Washington

+300

Winter Covid

surge

More deaths per week

than would be typical

Coronavirus

epidemic begins

+200

+100

0

2019

2020

2021

–100

Fewer deaths

Than typical

+300

Winter Covid

surge

Oregon

+200

Heat

wave

+100

0

2019

2020

2021

–100

Washington

Week of the

heat wave

+400

More deaths per week

than is typical

+300

Winter Covid

surge

Coronavirus

epidemic begins

+200

+100

0

2019

2020

2021

–100

Fewer deaths

than typical

+300

Winter Covid

surge

Oregon

+200

Heat

wave

+100

0

2019

2020

2021

–100

Source: Centers for Disease Control and Prevention·Deaths in recent weeks are most likely undercounted because of lags in reporting.

​​During the deadly heat wave that blanketed Oregon and Washington in late June, about 600 more people died than would have been typical, a review of mortality data for the week of the crisis shows.

The number is three times as high as the states’ official estimates of heat-related deaths so far. It suggests that the true toll of the heat wave, which affected states and provinces across the Pacific Northwest, may be much larger than previously reported.

This week, the region is once again steeling itself for extreme heat.

The New York Times’s analysis, based on mortality data reported to the Centers for Disease Control and Prevention by the two states, covers all causes of death, including Covid-19. But the public health agency’s initial calculations indicate that only about 60 deaths in the region were related to the coronavirus that week.

The figures are preliminary. C.D.C. officials said the death count could rise further in coming weeks as the states continue to report. “Consider it a floor,” said Lauren Rossen, a health statistician at the agency who works with the mortality data.

The Times’ estimate “is entirely consistent with a large body of knowledge indicating that days of extreme heat are dangerous and can lead to excess deaths,” said Greg Wellenius, a professor in environmental health at Boston University who has studied heat-related mortality.

Evaluating what are termed “excess deaths” — the number of deaths above what would have been typical for a given period of time, based on mortality rates in previous years — can provide a more complete picture of the effects of extreme heat than official counts of heat-related deaths. Those counts focus on the declared cause of death, for instance, heat stroke. But that can undercount other fatalities that might also have been related to the heat.

“When it’s really hot outside, deaths from heat stroke certainly increase,” said Kate Weinberger, an environmental epidemiologist at the University of British Columbia, “but deaths from all sorts of other conditions increase as well,” including from cardiovascular and respiratory disease.

Understanding the full consequences of extreme heat on mortality is important because it can help communities better plan for future heat waves, which are becoming more common. Heat deaths are largely preventable, said Kristie Ebi, a professor in the Center for Health and the Global Environment at the University of Washington. “The more we understand about these deaths, the better we can prepare.”

The Late June Heat Wave

British

Columbia

Canada

Wash.

Ore.

United States

Temperature

compared to average

–25°F

Average

+35°F

British

Columbia

Canada

Wash.

Ore.

United States

Temperature

compared to average

–25°F

Avg.

+35°F

Source: Goddard Earth Observing System model, NASA·The map reflects air temperature at 2 meters (about 6.5 feet) above ground level on June 27, 2020, compared to the average temperature for the same day between 2014 and 2020.

During the last week of June, temperatures in the Pacific Northwest climbed more than 30 degrees Fahrenheit higher than average, smashing records and bringing life-threatening conditions to an area not used to such extreme heat.

An analysis by an international team of climate researchers found that such an intense heat wave would have been virtually impossible without the influence of human-caused climate change.

Washington State has officially reported that 95 people died from heat-related causes during the week of the heat wave, but investigations are continuing. Oregon has confirmed 96 heat-related deaths so far.

But the states’ excess deaths figures — nearly 450 extra deaths in Washington, and nearly 160 in Oregon, which has a little more than half the population of its northern neighbor — suggest the official figures severely underestimate the heat wave’s effect on mortality.

Even amid the coronavirus epidemic, the spike in deaths reported by Washington was exceptionally large. More people in the state died during the week of the heat wave than during any other single week of the pandemic, according to the C.D.C. data.

Officials in British Columbia, just across the Canadian border, recently reported more than 400 heat-related deaths during the week of the heat wave — a stunning number closer in line with the excess-death estimate for Washington State. The province’s coroner service told the Times there were around 600 more deaths than would have been typical during the same period, but said the number could be incomplete.

Extreme heat disproportionately affects vulnerable populations, including older people, homeless people and those who work outdoors. Access to air-conditioning can be a life saver. A preliminary review of deaths during the heat wave in Multnomah County, Ore., which includes Portland, found that none of the 54 people who died had central air-conditioning.

“Not everyone can stay at home all day in an air-conditioned space,” Dr. Wellenius of Boston University said. “Not everyone can afford an air conditioner.”

Understanding the groups most at risk for heat-related death and where those deaths occurred can guide public health officials to better direct their resources, including where to set up cooling centers during future crises. That will require more detailed local analysis.

The New York Times excess deaths analysis is based on state-level mortality data published by the C.D.C. during the coronavirus epidemic. The Times has previously used the data to gauge the impact of the virus.

Public health researchers regularly use excess deaths to measure the effects of catastrophic events like extreme heat. A recent study by Dr. Weinberger and Dr. Wellenius estimated that about 5,600 deaths nationwide could be attributed to elevated temperatures each year. That number is significantly higher than the 700 heat-related deaths per year officially estimated based on reported causes of death.

But deaths are only one measure of the heat wave’s impact on health. Though heat-related deaths disproportionately affect older people, high temperatures can make people of all ages sick and lead to hospitalizations.

An analysis made public last week reported a sharp rise in emergency department visits in the Pacific Northwest during the heat wave in late June. Between June 25 and June 30, nearly 3,000 emergency department visits were recorded for heat-related illness.

1,000

A Spike in Heat-Related Emergency Department Visits

During the

heat wave

In the Pacific Northwest

800

600

400

In 2019

In 2021

200

May 1

June 1

May 1

June 1

1,000

A Spike in Heat-Related Emergency Department Visits

During the

heat wave

In the Pacific Northwest

800

600

400

In 2019

In 2021

200

May 1

June 1

May 1

June 1

1,000

A Spike in Heat-Related Emergency Department Visits

In the Pacific Northwest

800

600

400

In 2019

In 2021

200

May 1

June 1

May 1

June 1

Heat-Related Emergency Department Visits

In the Pacific Northwest

800

600

400

In 2019

In 2021

200

May 1

June 1

May 1

June 1

Source: Morbidity and Mortality Weekly Report, C.D.C.·Data comes from the U.S. Department of Health and Human Services Region 10, which includes Oregon, Washington, Idaho and Alaska.

On June 28th alone, more than 1,000 heat-related visits to emergency departments were reported, compared with fewer than 10 visits during the same period in 2019.

Yet, researchers said the rapid analysis very likely underestimates the full impact of the heat. (They relied on a keyword search to identify heat-related emergency department visits that might miss some cases and did not capture visits to other sites where patients might seek care, such as urgent care centers.)

When temperatures rise, people can become severely ill, or even die, if the body is unable to effectively sweat and cool off. High humidity increases the risk, because sweat can’t evaporate as quickly. That can lead to an increase in internal body temperature, which can cause muscles and enzymes to stop working and organs to shut down.

Dr. Steven Mitchell, medical director for emergency services at Harborview Medical Center in Seattle, described heat-related illness as a usually “rare phenomenon” in the city. During the heat wave, Harborview and its affiliated hospitals treated at least 100 patients for heat-related illness. Dr. Mitchell, who has worked at Harborview for 15 years, said that before this year he couldn’t remember treating a single case of severe heat illness or heat stroke.

The demands on hospital staff and equipment, including ventilators, during the heat wave reminded him of the early days of the Covid-19 pandemic, Dr. Mitchell said. “In an unprecedented year, this is once again unprecedented.”