Traffic noise linked to high blood pressure

Reported September 15, 2009

NEW YORK (Reuters Health) - Sitting in traffic can get your blood boiling temporarily, but living near it might raise your risk of long-term high blood pressure, a new study suggests.

Researchers found that among more than 24,000 Swedish adults, those living near relatively noisier roads were more likely to say they had high blood pressure than those living in more peaceful surroundings.

Middle-aged adults with the highest traffic-noise exposure -- averaging more than 64 decibels -- were almost twice as likely to report high blood pressure as their counterparts living near the quietest roads. A similar pattern was seen among young adults, but not the elderly. (For comparison, normal conversation has a noise level of about 60 decibels.)

The findings, published in the online journal Environmental Health, add to evidence that chronic noise exposure may spell health trouble. Other studies have found, for instance, that people living near airports or working in noisy jobs have an increased risk of high blood pressure and heart attack.

The theory is that because noise essentially signals the body that it's in a stressful situation, chronic exposure may cause long-term increases in stress hormone production, heart rate and blood pressure.

The current findings do not prove that nearby traffic caused study participants' high blood pressure. But they suggest it might have been a factor in some cases, according to the researchers, led by Theo Bodin of Lund University Hospital in Sweden.

The researchers surveyed 24,238 adults between the ages of 18 and 80 about their health and lifestyle, and traffic data to estimate participants' average exposure to road noise at home.

Of adults ages 40 to 59, 28 percent of those with the highest traffic- noise exposure said they had high blood pressure, versus 17 percent of those living near the quietest roadways. Average exposure in the former group was more than 64 decibels, compared with less than 45 decibels in the latter.

When Bodin's team considered other factors -- like age, income and lifestyle habits -- they found that middle-aged adults living near the noisiest roads were nearly twice as likely to have high blood pressure.

The researchers found a similar pattern among people younger than 40 -- although the risks were not as high, and far fewer men and women that age had high blood pressure.

There was no link between traffic noise and high blood pressure among older adults. A possible reason, the researchers speculate, is that because older people often have multiple risk factors for high blood pressure, any effects of noise exposure may be relatively small and harder to detect in a study.

They call for more research into the potential health effects of noise pollution at all ages.

SOURCE: Environmental Health, online September 9, 2009.