Living next to a noisy highway can be annoying. The racket can also disrupt your sleep.

Too many bad nights' sleep can raise the risk of heart attack, high blood pressure and other ailments.

Curious researchers with the Centers for Disease Control and Prevention wondered how many people in F ulton County, Ga., where Atlanta is the county seat, are exposed to highway noise levels that have been shown to cause sleep disturbances. The answer: about 2.3 percent of the population, or more than 21,000 people, are likely to be exposed to noise that's highly disruptive to sleep.

"Good mental health and sufficient restful sleep are important," says James Holt, an epidemiologist and geographer with the CDC. A paper about the findings will be published in an upcoming issue of the American Journal of Preventative Medicine. "If we look at all the factors that affect our health and well-being, environmental noise is important," he says.

Unlike previous studies that looked at noise exposure by census tract or zip code, this study used sophisticated mapping programs to divide the county into blocks that are 90 meters square. The researchers determined the highway noise levels for each one.

This study is just one step in gauging the effects of environmental noise. For one thing, Holt and his colleagues only factored in highway noise and didn't take into account the din from airplanes, railroads, car stereos, screeching birds, crying babies and so on.

Also, Holt's team wasn't able to track the health outcomes of people who live in the affected areas. So, while there are models that can predict how noise affects health, we don't know for sure whether those 21,000 people in Fulton County are experiencing highway noise-induced insomnia.

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