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August 18, 2010

1 In 5 US Teens Suffers Hearing Loss

As many as 20 percent of U.S. adolescents have some amount of hearing loss, and the problem has worsened in recent years, according to a new study published Wednesday in the Journal of the American Medical Association.

"Teenagers really underestimate how much noise they are exposed to," said Dr. Josef Shargorodsky of Brigham and Women's Hospital in Boston, the study's lead researcher.    

"Often the individual won't notice it, but even slight hearing loss may lead to differences in language development and learning," said Shargorodsky during an interview with the Associated Press (AP).

Some experts have suggested that listening to loud music with earbuds may be behind the rise in teen hearing loss in recent years, and warn that even slight hearing loss can set the stage for problems later in life.

"Our hope is we can encourage people to be careful," said the study's lead author, Dr. Gary Curhan, also of Brigham and Women's Hospital in Boston.

The researchers analyzed data from two nationally representative surveys of 12- to 19-year-olds, comparing hearing loss in nearly 3,000 adolescents tested between 1988 and 1994 to nearly 1,800 kids tested between 2005 and 2006. 

The researchers found that the prevalence of hearing loss rose from roughly 15 percent to 19.5 percent between the first and second surveys -- a 31 percent increase.

When extrapolating the data to the entire U.S. teenage population, this equates to about 6.5 million teens with at least some loss of hearing.

The majority of the hearing loss was classified as "slight", meaning the teens were unable to hear sounds such as a whisper or rustling leaves, which typically occur at 16 to 24 decibels. 

Someone with a slight hearing loss "will hear all of the vowel sounds clearly, but might miss some of the consonant sounds" Curhan told the AP.

"Although speech will be detectable, it might not be fully intelligible," he added.

Females were significantly less likely than males to demonstrate any hearing loss in the 2005-2006 survey.   And histories of 3 or more ear infections, firearm use, and loud noise exposure for 5 or more hours per week were not significantly associated with any hearing loss in 2005-2006.

The researchers did not specifically name iPods or any other device as the culprit behind the rise in teen hearing loss, although they did notice a substantial increase in high-frequency hearing loss, which may suggest that noise had caused the problems.

They referenced an Australian study in 2010 that linked the use of personal listening devices with a 70 percent increase in the risk of hearing loss in children.

"I think the evidence is out there that prolonged exposure to loud noise is likely to be harmful to hearing, but that doesn't mean kids can't listen to MP3 players," Curhan said.

Kids today are listening to music twice as long as kids of previous generations, who used older technologies with shorter battery lives and less storage capacity, said Brian Fligor, an audiologist at Children's Hospital Boston.

Furthermore, kids today will sometimes set the volume on their digital players to levels that would exceed federal workplace exposure limits, Fligor told the AP.

Fligor conducted his own study of roughly 200 college students, and discovered that more than half listened to music at 85 decibels or greater, or about as loud as a vacuum cleaner. 

Consistently listening to music at such high levels can turn the microscopic hair cells within the inner ear into scar tissue, Fligor explained.

The researchers stressed the need for additional studies to better understand the underlying cause for the rise in teen hearing loss.

"Further studies are needed to determine reasons for this increase and to identify potential modifiable risk factors to prevent the development of hearing loss," they concluded.

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