Wildfire smoke hurts heart, not just lungs, new study finds

Wildfire smoke is bad for your lungs, but now scientists say it may be just as bad for your heart.

As rising global temperatures spark more and more intense fires, a new study out of UC San Francisco suggests smoke may rise as an even bigger problem for cardiovascular health in California — especially among its senior citizens.

“We think about smoking cigarettes as being related to heart disease in medical school,” said Zachary Wettstein, a graduating medical student at UC San Francisco and lead author of the study. “But it’s not a connection physicians typically make with air pollution in general.”

The research published Wednesday in the Journal of the American Heart Association comes as Californians are coping with some of the deadliest and destructive wildfire seasons in state history — and it may change how doctors think about wildfire smoke and heart health.

According to the study, people exposed to wildfire smoke are placed at higher short-term risk for conditions like heart failure, ischemic heart disease and stroke. The denser the smoke, the higher the risk. This effect is seen across all adults, but is most dramatic among those age 65 and older.

Wettstein and his colleagues reached their conclusion by looking at how many people checked into emergency rooms with heart complaints over the 2015 fire season. That year, more than 800,000 acres of northern and central California went up in flames and sent plumes of smoke billowing over the state. The researchers connected the dots between when and where the fires took place, how dense the smoke was each day, and how many people wound up in the ER with heart conditions afterwards.

The data showed that people made the most trips to the ER following days with the densest smoke, both for respiratory and cardiovascular conditions. Fewer checked in for either complaint on medium smoke days, and fewer

than that on light smoke days. On days of dense smoke, the rate at which older adults visited the ER for heart attacks went up 42 percent.

Scientists have a few competing theories as to how smoke exposure might contribute to heart disease. Wildfire smoke contains bits of particulate matter, and the more there are, the denser the smoke.

“What we think happens is that you breathe in the particles, they start an inflammation process in the lungs, and that causes inflammation around the body and can trigger a cardiovascular disease event,” said Joel Kaufman, a physician-epidemiologist at the University of Washington who studies how cardiovascular disease is impacted by environmental factors.

Other scientists think a percentage of the particles might be tiny enough to slip straight from the lungs into the bloodstream, he said, and damage the vascular system directly. Still others think smoke exposure may trigger a “fight or flight” response in the body, stressing it to the point of harming the heart.

Doctors always think about air quality when a patient has trouble breathing. But the thought usually doesn’t cross their minds when a patient has an irregular heartbeat or heart failure.

“When you see someone with a respiratory complaint, it’s very intuitive — you’re breathing bad air, your breathing sounds bad, and I therefore draw a connection between the two,” said Jahan Fahimi, a professor of emergency medicine at UC San Francisco and co-author of the study. Fahimi used to practice in Alameda County and said he witnessed an influx of asthma patients whenever there was a refinery fire.

“But you see someone comes in with a stroke, it’s not intuitive that bad air quality in the last few days actually caused it,” he said.

While there is plenty of evidence that poor air quality is a serious risk factor for respiratory conditions, far fewer studies have connected the dots to heart health. Most research that has been done focuses on the effects of pollution from the burning of fossil fuels, but the jury was out on how woodfire smoke might hurt the heart. Wettstein intended his study to help clear up the matter.

This research is as relevant to government officials as it is to health care practitioners. “Local and state officials might change their view of the potential health impact of these big wildfires in vulnerable populations,” said Wayne Cascio, lab director at the U.S. Environmental Protection Agency and coauthor of the study. To address the public health angle, officials may have to revamp policies surrounding forest management and fire prevention efforts, he said.

And of course, there’s another cost to consider with all those trips to the emergency room: the costs.

“Increased awareness and prevention,” Cascio said, “would have a benefit in lowering healthcare costs and the burden on society.”