People who live near traffic noise, especially when it continues at night, are more likely to develop the repetitive whistling or buzzing sounds in their ears known as tinnitus.
Danish researchers found a link between the risk of developing the condition and traffic noise, with a vicious cycle of stress reactions and sleep disturbance as a potential cause.
Living near a busy road may increase your stress and affect your sleep, they explained, and those who are sleeping poorly and have higher stress may be at greater risk for tinnitus.
For the study, the researchers used data from 3.5 million Danes, finding more than 40,000 cases of tinnitus.
For every 10 decibels more noise in people's homes, the risk of developing tinnitus increased by 6%, said researcher Manuella Lech Cantuaria, an assistant professor at the Mærsk Mc-Kinney-Møller Institute and affiliated with the department of clinical research at the University of Southern Denmark.
The need exists for more focus on the importance of traffic noise and human health, said researcher Jesper Hvass Schmidt, an associate professor in the department of clinical research and chief physician at Odense University Hospital.
Schmidt thinks there are likely even more unreported cases of tinnitus not referred to a hearing clinic by doctors.
Tinnitus is ringing, buzzing, whistling or humming sounds that don't come from an external source. It can be a sign of an underlying disease or injury, but can also have an unknown cause. It often occurs with hearing loss.
Tinnitus can have a negative impact on quality of life. Psychological treatment and hearing aids may help, the study authors noted.
The researchers suggested some prevention efforts to reduce noise in homes. A person could opt to sleep in a room that does not face the road or to install soundproof windows, they said.
That's not an option for everyone, so traffic noise should be considered a health risk taken into account during urban planning and political decisions, according to a university news release.
The study noted that it's a myth that electric cars can reduce traffic noise because the contact between the tires and the road is the main cause of noise. In Germany, speed limits have been lowered in some places at night as a way to limit sleep disturbances, the study authors said.
Another way to reduce noise is by placing barriers along the road or changing the road surface to one that dampens the tire noise.
More studies are needed so that researchers can determine whether traffic noise actually causes tinnitus, and how this happens.
The findings were published Feb. 1 in the journal Environmental Health Perspectives.