We've written plenty in the past about the benefits of listening to music. Unfortunately, not all sound enhances health and happiness in the way that music does. In fact, constant exposure to noise over time can impair health far beyond the obvious issue of possible hearing loss. A few years ago, studies found that airport noise increases the risk of stroke. Other studies have found that the type of quiet background buzz we hear in offices can impair cognitive function. And now, new research has determined that traffic sounds increase heart attack risk, and by a substantial margin.
The new study comes from Denmark, where scientists followed over 57,000 people for a 10-year period. After controlling for environmental and health factors, the researchers calculated how much exposure to traffic noise each of the participants experienced over the study period. They did this by using detailed histories of where the subjects had lived and worked. They found that for every 10 decibels of traffic noise exposure that the subjects lived with, their heart attack risk went up by 12 percent.1
The noise didn't need to be loud or even particularly close to create the negative impact. The adverse cardiovascular health effects started at around 40 decibels, the equivalent of a birdcall outside your window or the melodic babbling of a stream--not very loud at all.2 The highest measured exposure level was 82 decibels.3 That equates to typical city noise. According to an article in Time Heartland, "the sound of a passenger car traveling at 65 miles per hour measures 77 dB from 25 feet away."
Study director Mette Sorensen of the Danish Cancer Society says, "There doesn't seem to be a level where there are no effects." That's rather disturbing news, given that most of us have at least some traffic exposure where we live. For those who spend lots of time perched near a highway, the results present a good reason to move if possible, with a nearly 50 percent increased heart-attack risk.
Why does the sound of traffic impair cardiovascular health? Sorensen says, "One [factor] is that traffic noise disturbs sleep, and you can be disturbed without even realizing it. [Other kinds of stress may contribute] but we think that noise at night is most dangerous." In other words, it's the lack of sleep and consequent elevated blood pressure that causes the cardiovascular risk. The study did not consider other outcomes or health risks resulting from the noise.
The question arises of what other factors might be responsible for the results of this study. One obvious factor is that living on top of a busy roadway certainly brings more pollution into play. Earlier studies found a definite link between exposure to traffic pollution and elevated heart-attack risk, although at least one study last year found that the effect was transient, and dangerous mostly for those already at high-risk.4
In any event in this current study, the scientists did indeed control for traffic pollution as well as railway and airport noise. The results showed that the elevated heart-attack risk appeared even when other variables were controlled, so the effect seems to be directly related to noise. As the report says, "In conclusion, the present study shows a positive association between residential exposure to road traffic noise and risk for MI in a general Danish population, with a clear dose-response relationship."
So what does this mean given that we live in an increasingly noisy world? We go about our business with airplanes flying overhead, air conditioners whirring in our rooms, bulldozers leveling the ground next door so a mall can be built. Certainly, traffic noise isn't the only type of noise that undermines health.
As mentioned above, a German study a few years ago found a startlingly high correlation between exposure to airplane noise and stroke.5 In that research, men living in a flight path upped their chances of being hospitalized for cardiovascular disease by 69 percent; for women, the rate increased 93 percent. And the stroke rate for women who heard jet noise at about 60 decibels during the day escalated to 172 percent higher than women who lived in quiet areas. So much for the theory about the deleterious effects being merely the result of disturbed sleep.
What's the solution? First, be aware of how much noise exposure you get. If you're subject to an unusually high level of noise, you might start by getting a white noise machine or sound-canceling headphones. If that doesn't work, you can try counteracting the effects by playing Bach during the good times. And if none of those things get you any respite, and if the sound is constant and at a level higher than 60 decibels, you just might want to consider packing up and moving on.
1 Sorensen, Mette, et al. "Road Traffic Noise and Incident Myocardial Infarction: A Prospective Cohort Study." PlosOne. 19 September 2012. < http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0039283>
2 "Decibel Sound Ruler." TLC. < http://www.tlc-direct.co.uk/Technical/Sounds/Decibles.htm>
3 Gann, Cary. "Study Links Traffic Noise and Heart Attack Risk." 20 June 2012. ABC News. 19 September 2012. < http://abcnews.go.com/Health/noisy-traffic-linked-heart-attack-risk/story?id=16613762#.UFoy0K68Gso>
4 Melnick, Meredith. "Study: Traffic Pollution May Boost Your Risk of Heart Attack." 21 September 2011. Time Healthland. 19 September 2012. < http://healthland.time.com/2011/09/21/study-traffic-pollution-may-boost-your-risk-of-heart-attack/>
5 Moore, Tristiana. "Study: Airport Noise Increases Risk of Stroke." 15 December 2009. Time Specials. 21 September 2012. <http://www.time.com/time/specials/packages/article/0,28804,1929071_1929070_1947782,00.html>