Ravell Call
Smog blankets Davis and Salt Lake counties as an inversion lingers on Wednesday, Jan. 18, 2017.

SALT LAKE CITY — Building on research showing that periods of high air pollution are associated with increased risk of heart attacks, scientists at Intermountain Healthcare and BYU say they have found that people with some blood types are more susceptible than others.

People with A, B and AB blood types are especially at risk when there is at least 25 micrograms of particulate matter per cubic meter in the air, according to the organizations' study, presented Tuesday at an American Heart Association meeting in Anaheim, California.

"Prior studies didn't differentiate by blood type," said Benjamin Horne, a clinical epidemiologist at Intermountain Medical Center Heart Institute who led the study. "In the past, all the other studies have been just a general survey of all comers, regardless of what their DNA or blood type might tell us."

People with type O blood are also at an increased risk during high pollution, but not to the same extent, Horne said.

For every 10 micrograms of particulate per cubic meter in the air above 25, the risk for people with type A, B and AB blood increases by 25 percent above normal, while for blood type O blood patients, that incremental increase is just 10 percent, according to the results of the study.

During winter inversions on the Wasatch Front, air pollution can reach 100 micrograms per cubic meter on occasion, with that metric hitting 50 to 60 frequently, Intermountain Healthcare spokesman Jess Gomez said in a release.

"Along the Wasatch Front, we get these pollution events that you can't really get away from it unless you drive out of the city to get away," Horne said. "It also is across the entire population, so it's relatively involuntary if you're just going about your daily activities without thinking about it."

The study utilized data from more than 1,300 Intermountain Healthcare heart attack patients whose DNA was collected between 1993 and 2007, Horne said. Corresponding air pollution data was provided by C. Arden Pope III, a BYU economics professor, longtime air pollution expert and one of the authors of the study.

Several prior studies show a clear connection between heart attack incidents and air pollution overall, according to Horne.

"Really within the same day or one day after the rise in air pollution, there's an increase in heart attacks," he said.

Horne said people who have the "ABO gene" that gives them an A, B or AB blood type, aside from being more affected by air pollution, are considered to be at higher risk of heart attack in general among those who suffer from coronary disease.

More than 99 percent of people who have heart attacks suffer from that disease, he said, though the condition is far from a guarantee of a heart attack. Many people do not know they have a coronary disease prior to a heart attack, though it is possible to check for it with a doctor, according to Horne. Major risk factors for the disease include high blood pressure, diabetes, smoking, obesity and advanced age.

Even in a winter inversion, people at heightened risk of heart attack due to pollution have steps within their control to reduce the danger to themselves, Horne said. The study's conclusion "isn't something to panic over, but it is something to be aware of,” he said.

"There partly is a sense of not being able to do much individually" to stay safe during pollution, he said. "Part of what we're trying to do is get the right information … (that they) can have confidence they can do something about it."

What at-risk people can do is stay indoors on particularly bad days, especially for exercise, and vigilantly take their heart medication, Horne said.

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"Only about two-thirds of the time, and in some cases only half the time, do (heart patients) actually take their medications, even though the medications have been shown to save lives," he said.

Knowing precisely who is at risk "helps us to understand who to spend a little more time with … educating them and helping them or making certain they have the tools and understanding they need to prevent health events in the future," according to Horne.

"From a clinical perspective … a physician or nurse might want to spend a little more time with them to make sure they really understand what that risk means and how to ameliorate it," he said.