How the stressed brain boosts heart attack risk

Being stressed out increases our risk of heart disease and stroke, and the key to how to counter it may lie in calming the brain, a new medical study suggests.

Psychological stress has long been considered a source of sickness. But personal stress levels are difficult to measure and there isn't direct evidence of the link, even though population studies finger stress as a risk factor for cardiovascular disease just like smoking and hypertension.

"I think that this relatively vague or insufficient link reduced our enthusiasm of taking stress seriously as an important risk factor," said Dr. Ahmed Tawakol, a cardiologist at Massachusetts General Hospital in Boston.

Tawakol led a study published in Wednesday's online issue of The Lancet that sheds light on how the amygdala — a key part of the brain that is more active during emotional, stressful times —  is linked to a greater risk of cardiovascular disease such as heart attacks and strokes.

We have enough information to tell our patients that if they have cardiovascular disease and are subject to a high degree of stress to consider the possibility of looking for a stress reduction approach.- Dr. Ahmed Tawakol

The researchers gave 293 patients aged 30 or older without cardiovascular disease PET/CT brain imaging scans, mainly for cancer screening and followed them over time.

After an average of nearly four years, activity in the amygdala was significantly associated with cardiovascular events such as heart attacks, heart failure and strokes, after taking other factors into account. People with more amygdala activity also tended to suffer the events sooner, Tawakol said.

Active amygdala measures were also linked to increased bone marrow activity and accelerated thickening of the arteries. The findings shed light on a biological path of how stress can turn deadly.

"We have enough information to tell our patients that if they have cardiovascular disease and are subject to a high degree of stress to consider the possibility of looking for a stress reduction approach," Tawakol said.

Lowering stress can be as simple as practising mindfulness, which he said has been shown repeatedly to reduce amygdala activity. As well, a recent randomized trial of 226 individuals who were assigned to standard cardiac rehab or the rehabilitation plus stress reduction showed cardiovascular disease events were cut nearly in half over five years with the stress buster training.

Watch reaction to stress

Stress plays an important role in heart attacks caused by a blockage in the heart, said Dr. Chi-Ming Chow, a cardiologist at St. Michael's Hospital in Toronto and a Heart & Stroke spokesman. He wasn't involved in the research.

Stressful periods such as war, extreme hot or cold, and even swings in the Shanghai stock market have been correlated with more heart attacks, Chow said.

"It's really how we react to stress that actually matters," Chow said.

Chow recalled classic research from the 1960s when doctors established the "Type A personality" — for instance, when physicians see a nervous patient sitting on the edge of their chair. 

It's important to recognize stress and to take it easy to prevent yourself from reacting excessively to stress, Chow said. He recommends people find support by talking to family and friends and exercising. 

The data establishes a connection between stress and cardiovascular disease and identifies chronic stress as a true risk factor for acute cardiovascular syndromes, Ilze Bot and Johan Kuiper of the biopharmaceuticals division at Leiden University in The Netherlands said in a journal commentary published with the latest study.

Tawakol's current and previous studies had a limited number of patients, and activity in the amygdala wasn't measured in healthy controls, the commentators said.

But the research "provides important evidence," although indirect, to justify new studies in larger populations and longer followup. The commentators suggested assessing cardiovascular risk directly in patients with PTSD for example.

There was no funding for the study. Tawakol has received funding and fees from pharmaceutical companies for other research projects.