Exercise reduces heart disease risk by altering the brain's response to stress

A new study suggests that physical activity, by affecting stress and related moods, may protect against cardiovascular disease (CVD).

The study, published in Journal of the American College of Cardiology and conducted by researchers at Massachusetts General Hospital, involved analyzing medical records from the Mass General Brigham Biobank of more than 50,000 people who completed a physical activity questionnaire.

A smaller group of 774 study participants also had brain imaging tests to measure stress-related brain activity.

After a 10-year average follow-up period, the researchers found that 12.9% of participants developed CVD. Those who reached recommended levels of exercise had a 23% lower risk of developing CVDs compared to those who did not reach these levels.

Researchers found an inverse relationship between physical activity and stress-related brain activity: higher levels of exercise led to lower levels of stress-related brain activity. People with stress-related brain conditions, such as depression, benefited significantly more from physical activity.

According to Dr. Ahmed Tawakol, one of the researchers and a cardiologist at the Center for Cardiovascular Imaging Research at Massachusetts General Hospital, exercise was "about twice as effective in reducing the risk of cardiovascular disease among those with depression."

What is the prevalence of heart disease in people with depression? According to the World Health Organization, cardiovascular disease is the leading cause of death in the world, with an estimated 17.9 million deaths in 2019; 85% of these deaths were due to strokes or heart attacks. More than 75% of these deaths occur in low- and middle-income countries.

Depression affects approximately 280 million people worldwide, according to the WHO. Not surprisingly, depression can lead to CVDs as a result of many related behaviors, such as unhealthy relationships with alcohol, sugar or processed foods.

Chen Cheng-Han, MD, a board-certified interventional cardiologist and medical director of the structural heart program at MemorialCare Saddleback Medical Center in Laguna Hills, California, who was not involved in the study, told Medical News Today that the link between SWD and depression is symbiotic. He said there are a number of other stress-related conditions that can create a favorable environment for the development of SWD.

"There is a strong link between depression and cardiovascular disease, a link that is two-way. About a quarter of people with cardiovascular disease experience depression, and many people with depression develop heart disease," Chen said.

"In addition to depression, other mental disorders associated with cardiovascular disease include anxiety and PTSD. People with depression may experience elevated blood pressure and physiologic stress, which are risk factors for heart disease. They may also be more likely to adopt lifestyle changes, such as smoking and physical inactivity, which may further increase their risk of developing cardiovascular disease," he told MNT.

Dr. David Merrill, MD, PhD, a geriatric psychiatrist and director of the Pacific Brain Health Neuroscience Institute at Providence Saint John's Health Center in Santa Monica, California, who was also not involved in the study, reported that stress-related brain activity can lead to a number of problems in other parts of the body, many of which are linked to depression.

He emphasized the two-way link between depression and heart disease.

"The link is two-way, with depression leading to higher rates of CVD. Anxiety similarly leads to higher heart rate and blood pressure, along with increased cortisol levels, all of which increase the risk of CVD. Both depression and anxiety lead to unhealthy behaviors such as smoking and sedentary lifestyles. In contrast, exercise has an anti-inflammatory effect that is cardio-protective," Merrill said.

Exercise may offer more benefits than medication for depression

Many medications for depression work by increasing neurotransmitters in the brain that can affect behavior and mood. Serotonin reuptake inhibitors (SSRIs) such as Lexapro or Prozac are commonly prescribed for depression, while serotonin-norepinephrine reuptake inhibitors (SNRIs) such as Cymbalta or Pristiq can be used to treat other anxiety disorders.

But exercise can counteract depression and stress-related brain activity in a variety of ways by naturally affecting brain chemistry: regulating appetite hormones, reducing inflammation, decreasing stress, and increasing metabolism.

Chen said the effects of exercise can be seen chemically in the brain, but physical effects on the body are important in reducing the development of CVD.

"We believe that exercise changes brain chemistry to promote the growth of growth factor proteins that form new connections in the brain, especially in the hippocampus, which improves people's mood. Of course, exercise provides significant other benefits to the underlying physiology of the body that may reduce a person's chances of developing heart disease," Cheng-Han Chen, MD

"It is possible that the decrease in stress-related brain activity in people with higher levels of physical activity is due to endorphins produced by more intense exercise," Chen explained.

Dr. Merrill added that "it turns out exercise is good for the heart at least in part because of its effect on the brain."

"Unlike serotoninergic antidepressants, physical activity increases activity in the prefrontal cortex, which improves mood. Greater activity in the prefrontal cortex, in turn, reduces stress-related hyperactivation of the autonomic nervous system. Exercise also increases brain-derived neurotrophic factor, which improves mood through changes in brain plasticity," Merrill said.