MP3 Generation: Noise-induced hearing loss rising among children and adolescents

With the increasing use of iPods and other MP3 players, more and more children and adolescents are putting their hearing at risk. Prior to the introduction of MP3 players, hearing loss among children was estimated at around 12.5 percent. More recent studies, however, estimate that 16 percent of teenagers, or approximately 6 million children, suffer from permanent noise-induced hearing loss (NIHL).

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January 2010

And the problem may only get worse. “We are still in the infantile stages of NIHL,” said Roland D. Eavey, MD, director of the Vanderbilt Bill Wilkerson Center for Otolaryngology and Communication Sciences at the Vanderbilt University School of Medicine in Nashville, Tenn. “It is a little like where we were with smoking in the early 1940s. Everyone thought it was glamorous, and soldiers were given cigarettes in their K-rations.” As with cigarette smoking, “after a while it is going to become painfully obvious that use of MP3 players is damaging, and it will be too late to reverse the hearing loss,” he said.

NIHL is already a problem for many baby boomers weaned on rock concerts. “The baby boomer generation has 26 percent more hearing loss than that of the senior population,” noted Marcella Bothwell, MD, chair of the Pediatric Airway and Aerodigestive Team at Rady Children’s Hospital of San Diego.

So where do otolaryngologists fit into this issue? Experts interviewed by ENT Today agreed that otolaryngologists need to not only screen children and adolescents for hearing loss but also educate them about causes of NIHL.

Lack of Awareness

At the heart of the problem is a lack of awareness among adolescents that their music listening behavior may have dire long-term consequences. To measure the pulse of American adolescents, Dr. Eavey and colleagues conducted a Web-based survey in 2002 and then repeated the survey five years later to see if attitudes about loud music had changed. The two surveys wereconducted through Music Television’s Web site (MTV.com).

The first survey, which included analysis of 9,693 Web surveys, found that only 8 percent of respondents felt that hearing loss related to listening to loud music was “a very big problem.” Adolescents consistently rated other health issues as bigger problems than hearing loss: sexually transmitted disease, 50 percent; drug/alcohol use, 47 percent; depression, 44 percent; nutrition and weight loss, 31 percent; and even acne, 18 percent (Pediatrics. 2005;115(4):861-867).

The first survey was notable, Dr. Eavey told ENT Today, because most of the respondents said they had experienced tinnitus or hearing impairment after attending a concert (61 percent) or going clubbing (43 percent). At the time of the survey, only 14 percent of respondents had used earplugs. When asked if they would consider wearing ear protection if they were aware of the potential for permanent hearing loss, 66 percent of the respondents said yes, while 59 percent said they would do so if advised by a medical professional.

We should be asking all our patients about their listening habits: Do you listen to an iPod? Are you aware that listening to your iPod at high volumes can cause permanent hearing loss? We have that responsibility.
—Marcella Bothwell, MD

Enter the MP3 Player

At the time of the first MTV survey, “MP3 players were not even on the radar screen,” noted Dr. Eavey. Apple first introduced the iPod in October 2001. As of September 2009, Apple reported that close to 225 million iPods had been sold and that they controlled 74 percent of the market share in personal music players. Introduced with the iPod were “ear buds,” earphones that direct music straight into the ear canal.

To survey the effect of MP3 players, which typically use ear buds, Dr. Eavey and colleagues added questions about personal music players to their 2007 MTV survey. This time the investigators received 2,500 responses. “Hearing loss was considered a problem by 32 percent of respondents compared with other health issues such as drug/alcohol use [62 percent],” they reported (J Pediatr. 2009;155(4):550-555).

In addition, the researchers found that 75 percent of respondents owned an MP3 player, and 24 percent listened to music players for more than 15 hours per week. The researchers also surveyed how loudly respondents played their MP3 players; 45 percent of respondents indicated that they listened at 75 percent to 100 percent of volume capacity. Researchers have known that it only takes one hour of listening to an MP3 player at 70 percent of maximum volume to reach “the maximum permissible noise dose recommended by government regulation for occupational sound levels. If these were factory workers, they would be beyond [Occupational Safety and Health Administration] regulations,” Dr. Eavey said. “These kids do not have anybody punching the clock for them. There is nobody there to tell them to turn it down or off.”

In addition, 89 percent of respondents noted that if ambient sounds were loud—subway or street noise, for example—they would turn the music up to compensate. “To hear your iPod over that noise, you have to increase the volume by about 10 db [decibels] more, so that is putting it at 100 db level. Rock concerts are 120 db,” Dr. Bothwell noted.

Most people with mild high-frequency hearing loss are unaware of their impairment.
—Ineke Vogel, PhD

The 2007 survey also found that nearly half of respondents had experienced some form of ear problems. Most had experienced tinnitus (77 percent), trouble hearing (40 percent), and ear pain (34 percent) after exposure to loud music. But despite having symptoms of hearing loss, only 15 percent used earplugs when going to concerts or clubs. The good news was that once made aware of the dangers of loud music and playing MP3 players too loudly or over long periods of time, 35 percent of respondents revealed a willingness to adopt ear protection—either earplugs or noise-canceling earphones.

A 2009 Dutch study led by Ineke Vogel, PhD, postdoctoral researcher at the Department of Public Health at Erasmus Medical Center in Rotterdam, noted that adolescents often underestimated their own vulnerability (Pediatrics. 2009;123(6):e953-e958). The investigators found that frequent MP3 player users were four times more likely to listen to high volume music than were infrequent users. “A plausible explanation for this underestimation might lie in the gradual development of hearing loss,” Dr. Vogel told ENT Today in an e-mail. In addition, her study found that adolescents “showed no understanding of how to determine which volume was too loud.”

By the NUMBERS: Whisper(30 db), Normal conversation (60 db), Street noise (80-90 db), iPod Shuffle (115 db), Rock concert (120 db)

Screening Falls Short

Most hearing tests performed in pediatrician and family practice offices are not sophisticated enough to catch the early signs of NIHL, experts said. “Even our standard hearing tests do not pick up on NIHL until it is too late,” Dr. Bothwell said. This is because the hearing loss caused by NIHL starts at the higher frequencies—16,000 hertz. “By the time you get hearing loss that is detected by most screening techniques [up to 8,000 hertz], the child is well on their way to irreversible damage,” Dr. Bothwell added.

Researchers have begun to study the effects of MP3 players on cochlear function using transient-evoked otoacoustic emissions (TEOAEs) and distortion-product otoacoustic emissions (DPOAEs). In one study, researchers from the Basurto Hospital in Spain found that cochlear impairment can be detected “by a reduction in TEOAE and DPOAE and an increase in DPOAE threshold.” The investigators noted that use of MP3 players is associated with cochlear impairment. The possibility of early detection of hearing alteration by OAEs may allow physicians to warn patients about the risks of hearing loss before it is too late, they concluded (J Otolaryngol Head Neck Surg. 2008;37(5):718-24).

A second study, led by Shaum P. Bhagat, PhD, an assistant professor at the School of Audiology and Speech-Language Pathology at the University of Memphis in Memphis, Tenn., looked at DPOAEs and synchronized spontaneous OAEs before and after a 30-minute MP3 session at 85 db (Int J Audiol. 2008;47(12):751-760). The investigators found that a comparison of pre- and post-exposure levels revealed no significant difference in hearing thresholds, but DPOAE levels were “significantly reduced following music exposure.” According to the study, “the results indicate that changes in OAEs may precede the development of music-induced hearing threshold shifts.”

Only 15 percent of  adolescents say they use earplugs at clubs or concerts.

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Only 15 percent of adolescents say they use earplugs at clubs or concerts.

Missing Link: Education from Otologists

Otolaryngologists may be missing out on an opportunity to educate patients about NIHL, according to Dr. Bothwell. “We should be asking all our patients about their listening habits: Do you listen to an iPod? Are you aware that listening to your iPod at high volumes can cause permanent hearing loss? We have that responsibility.”

In addition to adding questions about listening habits to a medical history, Drs. Eavey and Bothwell said the best way to reach adolescents is through a high-profile public awareness campaign, similar to the one designed to prevent drunk driving.

One program that has succeeded in reaching children has been “Dangerous Decibels” from the University of Oregon. A study of 478 fourth-grade students and 550 seventh-grade students found that students who underwent the Dangerous Decibels education program had “significant improvements in knowledge and attitudes related to hearing and hearing loss prevention” (Am J. Audiol. 2007;16(2):S165-181). The investigators, led by William H. Martin, PhD, professor of Otolaryngology/Head and Neck Surgery at Oregon Health & Science University in Portland, noted that the improvements were maintained three months after the program,” they added.

“We want to target teens because, frankly, their life span is longer than adults, and the impact of the hearing loss will be longer,” Dr. Bothwell said. As children and adolescents age, these deficits will be felt both in the workplace and social relationships, Dr. Bothwell added.

Now for the Good News

As a result of a 2006 lawsuit, Apple placed parental controls on iPod models, allowing parents and caregivers to set maximum volumes. Apple has also included information on NIHL on their Web site (www.apple.com/sound), but access requires the user to search the site for “noise-induced hearing loss” to find the information. In France, legislators have imposed a maximum volume of 100 db on all MP3 players sold in the country, and clubs and discos are required to sell earplugs.

Despite these efforts, Dr. Bothwell noted that otolaryngologists and other physicians should not rely on manufacturers or legislation. “We have a unique relationship with kids—they trust us. We have a responsibility to educate them that if they listen to music at 100 db three hours per day, they are going to get hearing loss,” she said.

Dr. Eavey agreed. “Once children become aware, they will change their behavior—it will become a habit just like applying sunscreen, wearing seat belts, and having a designated driver,” he said. ENTtoday

Cornelia Kean is a health writer based in Montclair, NJ.

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