Ask the Doctors by Eve Glazier, M.D. and Elizabeth Ko, M.D

Noise Pollution Causes Sharp Increase in Stress Hormones

Dear Doctor: My son just got a job working construction in Houston, which means he's surrounded by noise pretty much all the time. A family friend says he read that all that noise might be bad for my son's health, including his heart. Just how strong is the connection between heart disease and noise pollution?

Dear Reader: When it comes to noise being bad for us, your friend is correct. Decades of research have suggested a strong connection between ongoing exposure to noise pollution and a host of adverse health outcomes. These range from feelings of annoyance and tension, to increasingly significant problems like sleep and anxiety disorders, depression and cognitive impairment, particularly in children. Now, after an analysis of years of existing data, researchers from Johannes Gutenberg University in Germany confirm what previous studies have suggested -- that hypertension and cardiovascular disease also belong on the list.

Inquiry into the physiological effects of noise dates back at least to the 1980s. Those earlier studies focused solely on the effects of traffic noise, including road sounds, horns and sirens. Later studies added the effects of aircraft and railway noise into the mix. Scientists found that exposure to noise pollution resulted in an increase of blood and saliva concentrations of cortisol, adrenaline and noradrenaline in the study subjects. Chronic high levels of these stress hormones are known to play a role not only in heart disease, but also in immunity, hypertension and stroke. Individuals appear to be particularly vulnerable to the ill-effects of noise pollution at night, during sleep.

In this most recent review paper, published earlier this year in the Journal of the American College of Cardiology, researchers connected seemingly minor responses to noise pollution to the most serious outcomes. Each honk of a horn, scream of a siren or screech from a train track is met with a corresponding spike in stress hormones, heart rate and blood pressure. Even when individuals become outwardly inured to the ongoing sounds of traffic or aircraft, their bodies are mounting a stress response. Over time, the thinking goes, the cumulative effect takes a toll on the body at the cellular level.

When it comes to your son, he faces the effects of noise pollution at his workplace and, if he lives in the city, at home. While he's at work, he should use a hearing protection device like ear plugs, or ear muffs with soft cushions that fit around the ear and hard outer cups to help block out sound. If his construction company doesn't supply either of these, he should invest in high-quality gear of his own. This will safeguard his hearing as well as offer a measure of protection against the constant barrage of noise.

At home, using a white noise machine at night can help filter out some of the sounds that would otherwise produce a startle reflex. Noise-canceling headphones -- the technology has become advanced enough that you can create a virtual cone of silence -- can also offer protection.

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