A new brain study might help explain why a high level of stress is linked to an increased risk of heart attack and stroke.
Increased activity in the amygdala — the fear center of the brain — appears to create an immune system reaction that increases inflammation in the arteries, researchers plan to report at the upcoming American College of Cardiology meeting in Chicago.
Such arterial inflammation is a precursor to heart disease, heart attack and stroke, said senior researcher Dr. Ahmed Tawakol, a cardiologist at Massachusetts General Hospital in Boston.
Tawakol and his colleagues followed nearly 300 people and found their amygdala activity — as seen on brain scans — indicated whether they would suffer a major cardiac event in the near future.
“By the end of the study, roughly 5 percent with low activity had events, compared to roughly 40 percent of the individuals with high amygdala activity,” Tawakol said.
Doctors need to be aware of the heart-health consequences of current events such as the Syrian crisis and this week’s terror attacks in Brussels, said Dr. Richard Becker, director of cardiovascular health and disease at the University of Cincinnati College of Medicine. He is also director of the university’s Heart, Lung & Vascular Institute.
“After there’s an earthquake or a tsunami, the incidence of heart attacks over the next six to eight weeks increases substantially,” said Becker, an American Heart Association spokesman, citing prior research. “The same thing happens with human disasters, with terrorism, particularly if it’s on a large scale.”
Evidence of the strong link between stress and heart disease has been mounting. The heart-health risk posed by stress is now believed to be on par with factors like smoking, cholesterol, high blood pressure and diabetes, Tawakol said.
But little is known about how stress from anger, hostility, hopelessness or uncertainty might directly affect the heart, Tawakol said.
Animal studies have suggested that stress can cause bone marrow to release inflammatory cells, which then increase inflammation in the arteries, he said.
To see whether that happens in humans, researchers examined PET/CT scans for 293 patients, average age 55, who originally received the test between 2005 and 2008 for cancer screening but were found to be cancer-free.
The scans allowed researchers to measure activity in regions of the brain, the bone marrow and arteries. Patients were excluded if they had evidence of cancer, established heart disease or were younger than 30 years old.
During the five-year study, 22 patients experienced a heart attack or stroke.
Researchers found that increased amygdala activity meant greater activity in the bone marrow and increased inflammation in arteries.
Further, amygdala activity was linked to an increased risk of heart attack or stroke. Patients experienced a 14-fold greater risk of heart attack or stroke for every unit increase in measured brain stress activity, researchers said.
The amygdala also affected the timing of a heart attack or stroke. “Individuals with an event within a year after imaging had the highest amygdala activity values,” Tawakol said. People with the lowest amygdala activity went the longest before suffering a heart attack or stroke, the study found.
Becker praised the study.
“They [the study authors] were able to connect the dots from the brain to inflammation in the blood vessels to cardiovascular events,” Becker said. “This is a very important contribution to helping us understand what stressors really mean to human health.”
These findings show the importance of stress relief in a person’s life, be it through meditation, exercise, friendships or humor, Becker and Tawakol said.
“For primary care physicians and cardiologists, we need to be more cognizant of how to gauge a patient’s stress,” Becker said. “We’re very good at picking up when blood pressure is high and whether someone has diabetes, but we need increasing rigor in detecting a person’s stress.”
But the study also hints at new strategies to head off stress-related heart attacks, the researchers said. For example, animal studies have shown that some beta blockers can reduce the amount of inflammatory cells produced by the bone marrow in response to stress, Tawakol said. However, knowing whether those results would be replicated in humans is a long way off.
Data and conclusions presented at meetings are usually considered preliminary until published in a peer-reviewed medical journal.