More people along the Wasatch Front seek medical care for heart attacks and unstable chest pain when fine particulate pollution levels are high. In summer, that’s due to wildfires and in winter because of inversions.
But the risk and patient behavior are different for the two heart-related conditions depending on the season, according to a study by Intermountain Health researchers that’s being presented in Philadelphia this weekend at the American Heart Association’s international scientific sessions conference.
While the Wasatch Front, which stretches from Ogden south to Provo and includes Salt Lake City, has pollution from wildfires, the smoke typically reaches residents from farther away, said Benjamin Horne, who directs cardiovascular and genetic epidemiology for Intermountain Health at Intermountain Medical Center and was the study’s lead author.
Winter inversions are another story, caused by humans because of car exhaust and factory output, among other sources, and people are right in the thick of it.
June through October is wildfire season, while inversions come during November through March.
It’s long been known that air pollution contributes to heart disease and death and that not breathing in fine particulate PM2.5 pollution is important. The study was designed to see the difference between the two seasonal types of pollution. And it delivered some surprises.
Researchers found that in winter, people immediately seek help for a heart attack, but wait as much as two weeks to get help for unstable chest pain, even though untreated it’s likely to lead to a heart attack.
In summer, that unstable chest pain immediately triggers someone to seek medical attention. But researchers found no significant increase in people being admitted to hospitals for heart attacks. It’s possible that getting help for the unstable chest pain prevented the full-blown heart attack, Horne told the Deseret News.
Is there a behavioral reason, the researchers ask, that people with unstable chest pain wait two weeks to seek medical care during a winter inversion, while they seek it immediately during summer’s wildfire pollution?
PM2.5 and pain
Utah’s wildfires are typically to the east and the smoke blows east, so the particulate pollution from wildfires on the Wasatch Front typically comes from somewhere else, like California or Oregon. Recently, much of the smoke came from fires in Canada.
Wildfire is more subtle than inversion pollution. And the weather’s nicer, so more people are outdoors, instead of hunkered inside out of the cold.
Horne said that PM2.5 levels are typically lower from summertime wildfires, compared to the PM2.5 pollution seen in winter inversions. Still, how people respond to the pain they can cause is quite striking.
“With a heart attack, you feel crushing chest pain, have a hard time breathing and you immediately go to the hospital,” Horne said. But the unstable chest pain usually happens when people are not exerting themselves and patients sometimes second-guess what’s happening. In winter, they don’t seek help immediately, but wait to see if the pain goes away on its own. If it doesn’t, they seek care, sometimes two weeks after the unstable chest pain began.
Horne said during inversions, it’s easy to learn how good or bad the air quality is. It’s announced using a color-coded system where green is not a health risk, yellow is vulnerable folks beware and orange is risky for sensitive people. That category includes those with heart or lung disease, children and teens, people active outside and older adults.
When it’s red, no one is safe from potential health risks.
“Earlier research found most of the risk of heart attack from elevated PM2.5 is among those with existing coronary diseases, which they may not know they have. Sometimes a heart attack is the first symptom,” said Horne. “If they know, they should be more careful. Exercise indoors, take medicine, etc., according to prescription so they have additional protection.”
The study findings
“Most of the study period, wildfire smoke was notably less than the PM2.5 measured during inversion,” Horne said. Yet when someone feels unstable chest pain in summer, the quest to find help is quick. Horne said they act like they do with heart attacks during winter inversions.
For the study, the researchers looked at hospital visits and admissions at 11 hospitals on the Wasatch Front, comparing those to the pollution levels on the day of the hospitalization, as well as two weeks before. They also compared the data to days in the same month when people were not admitted to the hospital, to tease out PM2.5 pollution’s impact on health.
The study looked at records from 22,000 adults treated for heart attack or unstable chest pain between 1999 and 2022. The sample averaged age 66, most were male and 89% were white. The study also controlled for individual-specific factors including whether the person smoked, and chronic conditions like high blood pressure and Type 2 diabetes.
The study showed that for those with unstable chest pain in summertime, the same-day risk of hospitalization was roughly 45% higher during orange-level air quality, compared to when air quality was at green level.
Air pollution from a wildfire doesn’t dissuade people from working and playing outdoors, Horne said, though he wishes they’d be more cautious. Wildfire smoke is largely viewed as an annoyance and “not something that stops an outdoor activity. We’ve been recommending for almost 20 years, since the first study of air pollution and heart attack, that if there’s air pollution, go indoors.”
And it usually doesn’t come with green-yellow-orange-red warnings.
The researchers emphasize that waiting in winter may turn unstable chest pain into a heart attack, which kills heart muscle and can be deadly. Seeking help for unstable chest pain in summer may avert heart attacks, which could be why the latter’s numbers are lower.
They’re still trying to sort out the “why” of the different behaviors.
“Our hope is that in the community and the medical field, people and physicians will be more aware of potential risks in summertime. And if there’s substantial wildfire smoke, be more judicious about being outside. If there’s elevated PM2.5, exercise indoors,” Horne said. “Certainly people diagnosed with coronary disease or other heart diseases should take preventive measures and be aware.”