Age, diet, and lack of exercise are all obvious factors that can lead to a heart attack, but a new study finds something that most people probably don’t think about: road noise.
The study, conducted in Denmark by the Danish Cancer Society, found that every 10-decibel increase in traffic noise raised a person’s risk of having a heart attack by 12 percent. Researchers found that noise levels as low as 40 dB started to affect a person’s health. Forty dB is “as loud as a bird call or the inside of a library,” Time says, while a car traveling 65 mph produces 77 decibels of road noise from 25 feet away.
The 10-year study included 50,000 men and women ages 50 to 64 living in Copenhagen and Aarhus. Researchers monitored the participants’ health and accounted for factors including diet, exercise, air pollution, gender, weight, and where they lived. Exposure to road noise was analyzed based on traffic patterns surrounding the participant’s home.
During the study, 1600 participants experienced a heart attack. Researchers found that the heart attack victims increased their risk the louder road noise was to their homes. Why might that be? Residents in urban areas sometimes experience more stress, and the road noise could also affect sleeping patterns, robbing people of a good night’s rest.