Previous research has shown that chronic emotional stress is associated with an increased risk of cardiovascular disease. But until now, it wasn't fully understood how stress leads to physical events in the body that cause disease. A team of researchers led by a Massachusetts General Hospital physician recently found that stress triggers a number of conditions that can make someone more susceptible to a cardiovascular event, such as a stroke or heart attack.
The Amygdala Predicts Cardiovascular Events
The team was led by Ahmed A. Tawakol, MD, co-director of Mass General's Cardiac MR PET CT Program, who specializes in clinical cardiology, nuclear cardiology and noninvasive cardiovascular imaging. Dr. Tawakol and his team found that activity in a certain part of the brain, known as the amygdala, can predict future cardiovascular disease. The amygdala has been proven to play a big role in regulating responses to fear.
"With the amygdala as an entry point, we show for the first time in humans that stress prompts an increase in bone marrow activity and inflammation in blood vessels," Dr. Tawakol said. "This then sets the stage for cardiovascular disease to develop."
Dr. Tawakol's is the biggest longitudinal study that has compared brain imaging when the amygdala is at rest and disease outcomes. (In a longitudinal study, researchers repeatedly gather data from the same subjects over an extended period of time. In this case, none of the participants had heart disease when the study first began.)
The team at Mass General collaborated with researchers from Icahn School of Medicine at Mount Sinai, Tufts University and Weill Cornell Medical College to use positron emission tomography (PET) imaging to link imaging data with the characteristics of cardiovascular disease. A PET scan uses a special dye that contains a small radioactive substance picked up by organs and tissues. Parts of the body with high levels of chemical activity, which typically indicate the presence of disease, show up as bright spots on a PET scan.
When the researchers performed a brain image, they were able to measure the amount of activity in the amygdala. They found that amygdalar activity "predicted the development of cardiovascular disease events over the five years of follow-up," Dr. Tawakol said. When amygdalar activity increased, there was also an increase in bone marrow production and arterial inflammation. Together, these three events increased the risk of cardiovascular disease.
Reducing Stress Can Reduce the Risk of Heart Disease
With these new findings, physicians are focusing more of their efforts on the role of emotional stress in health and disease. Dr. Tawakol said he's now focusing on how patients can control stress using techniques such as mindfulness practices and exercise.
"Now with myself and my patients, I look at stress in medical terms—like an objective risk factor similar to LDL," Dr. Tawakol said. LDL, or low-density lipoproteins, is more commonly known as bad cholesterol and is one of the risk factors that can increase a person's chances of having a heart attack.
"If a patient has a high burden of chronic stress, there is a possibility that reducing his or her perception of that stress might lower the risk of heart disease," Dr. Tawakol said. However, he did note that the medical community still needs to conduct large-scale clinical trials to prove that reducing stress helps reduce a person's likelihood of developing heart disease.
The results of this study can also help physicians improve care for other conditions, but Dr. Tawakol said there is a lot left to learn about these new pathways. For now, though, these recent discoveries around the genetic aspects of stress can help physicians provide practical advice to patients on how to best manage their health.