Living or working next to a busy highway or airport may affect the brain in a way that raises your risk of cardiovascular events, such as stroke or heart attack.
In a study published recently in Environment International, researchers from Massachusetts General Hospital found that high levels of environmental noise exposure may fuel activity in a region of the brain associated with stress regulation. That, in turn, appears to raise the risk of cardiovascular disease.
“A growing body of research reveals an association between ambient noise and cardiovascular disease, but the physiological mechanisms behind it have remained unclear,” says study author Azar Radfar, MD, PhD, a research fellow at Massachusetts General Hospital. “We believe our findings offer an important insight into the biology behind this phenomenon.”
Dr. Radfar’s research was presented at the 2018 American Heart Association’s Scientific Sessions.
Stress and the Amygdala
To better understand how the stress of noise pollution might affect a person’s health, Dr. Radfar and her team of researchers analyzed 499 adults age 56 and older who had simultaneous positron emission tomography (PET) and computed tomography scans of their brains and blood vessels. Researchers then examined the medical records of the study participants. Within five years, 40 people in the study had a heart attack or stroke.
To gauge their exposure to noise pollution, researchers relied on the Department of Transportation and Highway Noise Map and matched that data to the study participants’ addresses. People with the highest noise exposure had more inflammation in their arteries and higher levels of activity in the amygdala, the part of the brain responsible for stress regulation and emotional responses. When the brain perceives stress, the amygdala sends a signal to another part of the brain called the hypothalamus. The hypothalamus communicates with the rest of the body through the autonomic nervous system, which controls your breathing rate, blood pressure, the dilation and constriction of certain blood vessels, and other responses throughout the body.
The study participants who had the highest noise exposure also had a three-fold higher risk of having a heart attack or stroke compared with the people who had lower levels of noise exposure.
That elevated risk was true even when researchers accounted for other factors that can affect stress and vascular inflammation, such as air pollution, smoking, high cholesterol and diabetes.
The researchers believe that stress triggers activity in the amygdala that then causes inflammation in the arteries, a major risk factor for stroke and heart attack.
While it’s not clear whether reducing noise exposure would also cut an individual’s cardiovascular risks, Dr. Radfar suggests that noise exposure not be overlooked when evaluating your risk of stroke or heart attack.
“Patients and their physicians should consider chronic noise exposure when assessing cardiovascular risk and may wish to take steps to minimize or mitigate such chronic exposure,” Dr. Radfar says.