"Exposure to traffic noise is believed to provoke a stress response and disturb sleep, which might increase the risk for stroke, through mechanisms including increased level of stress hormones, increased heart rate and blood pressure and impaired immune system," Sorensen said.
Researchers analyzed participants' medical and residential histories during an average 10-year period. A total of 1,881 suffered a stroke.
The researchers then measured their exposure to traffic sound over time using a noise calculation program designed to map noise levels in a variety of locations in Scandinavia for several years. The program takes into account a variety of factors that could amplify or blunt road noise, including traffic composition and speed, road surface and road type, nearby buildings and the position and heights of homes above the roads.
At the time the volunteers joined the study, 35 percent of them were exposed to noise levels greater than 60 decibels, and the majority (72 percent) lived at the same address throughout the study. Researchers estimated the lowest noise exposure to be 40 decibels and the highest to be 82 decibels.
They also accounted for a variety of other risk factors for stroke, such as air pollution, railway and aircraft noise, smoking, diet, alcohol and caffeine consumption.
The study is published in the current issue of the European Heart Journal.
The researchers "did a reasonable job of trying to control for other potential things that could affect the outcome," said Dr. Larry B. Goldstein, director of the Duke Stroke Center at Duke University in Durham, N.C.
However, Goldstein noted that there are likely a number of additional factors that could not have been accounted for. "These epidemiological studies are always subject to a variety of unmeasured biases that could potentially affect the outcome," he
All rights reserved