Exposure to road traffic noise boosts the risk of stroke for those 65 or older, according to research published online Wednesday in the European Heart Journal.
In a survey of more than 50,000 people, every 10 additional decibels of road noise led to an increase of 14 percent in the probability of a stroke when averaged for all age groups.
For those under 65, the risk was not statistically significant. But the risk was weighted hugely in the over-65 group, where it rose 27 percent for each 10 decibel increment.
Above 60 decibels or so, the danger of stroke increased even more, the researchers found.
A busy street can easily generate noise levels of 70 or 80 decibels. By comparison, a lawnmower or a chainsaw gives off 90 or 100 decibels, while a nearby jet plane taking off typically measures 120 decibels.
"Previous studies have linked traffic noise with raised blood pressure and heart attacks," said lead researcher Mette Sorensena of the Danish Cancer Society.
"Our study shows that exposure to road traffic noise seems to increase the risk of stroke."
The study reviewed the medical and residency histories of 51,485 people who had participated in the Danish Diet, Cancer and Health survey, conducted in and around Copenhagen between 1993 and 1997.
A total of 1,881 people suffered a stroke during this period.
Eight percent of all stroke cases, and 19 percent of cases in those aged over 65, could be attributed to road traffic noise, according to the paper.
The researchers suggest noise acts as a stressor and disturbs sleep, which results in increased blood pressure and heart rate, as well as increased level of stress hormones.
The study factored in the effect of air pollution, exposure to railway and aircraft noise, and a range of potentially confounding lifestyle factors such as smoking, diet and alcohol consumption.
The survey cohort lived mainly in urban areas and was thus not representative of the whole population in terms of exposure to road traffic noise.
Proximity to road noise is also related to social class, as wealthier people can afford to live in quieter areas.