Chronic exposure to environmental noise may increase the risk of a heart attack or stroke, according to a new study. The research suggests chronic noise stimulates the activity of a brain region involved in stress response, which in turn causes the inflammation of blood vessels.
The US researchers found people with the greatest degree of chronic noise exposure – such as airport and highway noise – were at a higher risk of suffering cardiovascular events such as heart attacks and strokes, regardless of other risk factors.
According to study author Azar Radfar, physiological mechanisms behind the association between cardiovascular disease and ambient noise have remained unclear until now. Radfar, who is a research fellow at the Massachusetts General Hospital in Boston, believes the preliminary findings “offer an important insight into the biology behind this phenomenon.”
Researchers analysed the association between noise exposure and major cardiovascular events among 499 people, all of whom had simultaneous PET and CT scans of their brains and blood vessels. The average age of participants was 56 years, and all were free of cardiovascular illness at baseline. Scientists monitored the activity of the amygdala, an area of the brain involved with stress regulation and emotional responses.
To understand the cardiovascular risk, the participants’ medical records were examined following the initial imaging studies. Of the 499 participants, 40 experienced either a heart attack or stroke in the five years following the initial testing.
Researchers used the home addresses of participants in order to gauge noise exposure, and derived noise level estimates from the Department of Transportation’s Aviation and Highway Noise Map.
Participants with the highest levels of noise exposure demonstrated higher levels of amygdalar activity and greater inflammation in their arteries. These participants were at three-times the risk of suffering a heart attack or stroke. This risk remained elevated even after researchers accounted for other risk factors, such as high cholesterol, smoking and diabetes.
Radfar said that until further researchers clarifies the link between chronic noise and heart disease, patients and physicians “should consider chronic noise exposure when assessing cardiovascular risk and may wish to take steps to minimize or mitigate such chronic exposure.”
A study published in the American Journal of Industrial Medicine earlier this year found a similar link between noise exposure and heart disease (see related article). Researchers at The National Institute for Occupational Safety and Health (NIOSH) found that employees exposed to high levels of ambient noise at work are more likely to develop high cholesterol and high blood pressure, both of which are major contributors to cardiovascular disease.
While researchers at NIOSH did not establish a direct cause and effect relationship between noise exposure and heart disease, employers could reduce the risk of high blood pressure and high cholesterol by implementing safer levels of noise in the workplace.