Blaring Sounds Leave Teen Hearing Unsound
THURSDAY, July 5, 2001 (HealthDayNews) -- If you're shouting at your kids, and they pay you no mind, it could be more than just youthful insolence. They may not hear you.
About 5.2 million American children might have damaged hearing from too much noise at way-high levels -- from rock concerts, stereo headphones, boom boxes, lawn mowers and leaf blowers, a new study suggests.
"This first-time study shows that children's hearing is vulnerable to hazardous noise exposure," says lead author Amanda Sue Niskar, a nurse epidemiologist with the Centers for Disease Control and Prevention's National Center for Environmental Health in Atlanta, Ga. "And what we all need to understand is that noise-induced hearing loss is a public health problem that is completely preventable, and people should be more aware of noisy activity. They should either avoid them or, if they choose to participate, they should wear protection."
Niskar and her colleagues analyzed data from more than 5,200 children and teens between the ages of 6 and 19 who took part in the third National Health and Nutrition Examination Survey (NHANES III) that was conducted from 1988 to 1994. The survey included household interviews and physical exams done in mobile centers. Included in the examination were two hearing tests -- one that tested how well they heard and one that looked for physical middle-ear problems.
"The survey was not done because of any specific problems, but was done to be able to describe the current health status of a representative sample of the American population," Niskar says. "It took several years for the data to be cleaned up and developed for analysis. And when it was ready in 1997, we got the idea that we should then go and look for a noise-specific audiometric pattern that could suggest hearing damage caused by loud noises."
Niskar and her colleagues found that about 12.5 percent of the those surveyed displayed Noise-Induced Hearing Threshold Shifts (NITS) -- a specific pattern that shows up on hearing tests. The pattern suggests hearing damage caused by loud noises -- in one ear or both ears. "When you see that pattern, it indicates that there is hearing damage specifically in the inner ear, because hair cells in the inner ear get damaged by loud noise. And when these hair cells get damaged, they don't grow back," Niskar explains.
Niskar says, however, that it's unclear what the lasting effect of such damage is. "We don't know if the damage we found during the testing was permanent, because the data was done at one point in time, and we don't know if people recovered."
The study showed that boys were at higher risk for hearing loss than girls, Niskar says. About 15 percent of boys showed NITS compared to 10.1 percent of girls. And the older they were, the more likely the NITS. More than 15 percent of 12-to-19 year olds had NITS patterns, while only 8.5 percent of those 6 to 11 showed the test pattern.
The differences between racial groups, socioeconomic groups and geographic groups "aren't statistically significant; they only indicate trends," Niskar says. "NITS is lower in females, and so it's possible that a difference in activities is the reason. Boys tend more than girls to participate in sporting events where there's lots of noise, or they go to NASCAR races or they ride motorcycles."
"And for the age group differences, it's definitely logical that older children are going to show more hearing loss because this damage accumulates over time," Niskar adds.
The findings are in the July Pediatrics.
"This is a noisy world, and it's getting noisier," says Les Blomberg, director of the Noise Pollution Clearinghouse in Montpelier, Vt. "So in a sense, it's a no-brainer that kids are showing up with this hearing loss. It confirms what we've suspected all along, that if you combine very noisy devices and activities with children, you're going to have some hearing loss."
"People need to recognize that this hearing loss occurs one noisy event at a time," Blomberg continues. "The solution to this problem is to start quieting those noisy events one at a time. In the interim, wear ear plugs when you go to a rock concert or you're blowing leaves or mowing the lawn."
"But the next time you buy a lawn mover, buy a quiet one," Blomberg advises."
What To Do
For more information on hearing loss caused by noise, see the American Family Physician. And check out the Noise Pollution Clearinghouse for the latest on the efforts to control environmental noise.