Boys have been more likely than girls to show signs of a particular type of hearing loss, but girls are catching up - and the ubiquity of portable audio players may be to blame, new research suggests.
Hearing tests conducted on a national sample of teenage girls and boys showed that now roughly 17% - or 1 in 6 - of teens of both sexes have hearing losses that can make it harder for them to hear speech and some high-pitched sounds.
"The girls have kind of just caught up with boys," study author Elisabeth Henderson of Harvard Medical School in Boston said.
The study, published in Paediatrics, didn't determine the cause of the hearing loss in girls, but one possibility, Henderson suggested, is that they are getting exposed to more loud noises.
Portable music players to blame
Traditionally, boys were more likely to be exposed to loud noises from leaf-blowers, firearms, or work machines, Henderson noted - but today, more and more teens have portable music players, and both sexes are listening to loud music from headphones.
Indeed, the authors found that the percentage of teens who said they had listened to loud music through headphones in the last 24 hours increased from 20% in the late 1980s and early 1990s to 35% in more recent years.
The kids who reported recent exposures were no more likely to show signs of hearing loss, but it's still possible that this increase in portable loud music is having an effect, perhaps explaining why girls have caught up to boys' levels of hearing loss, Henderson said in an interview.
"We're seeing a lot more kids being exposed to music recreationally," she noted.
To investigate whether the recent popularity of portable music players is affecting teens' hearing, Henderson and her colleagues looked at hearing tests collected from 2,519 teenagers between 1988 and 1994, and 1,791 teenagers between 2005 and 2006.
They considered three types of hearing loss: low-frequency loss, in which people struggle to hear sounds in the low end of the sound spectrum (such as parts of human speech); high-frequency hearing loss, which affects how well they hear high pitches (such as chimes or a microwave beep, or even kids' speech); and noise-induced hearing-threshold shifts, or "NITSs," in which people have trouble hearing sounds in the middle of the sound spectrum (which can include some human speech and higher-pitched sounds from musical instruments).
The investigators found that all three types of hearing loss were generally as common in the recent group of teens as they had been during the previous survey.
But when they looked more closely at the data, they saw that one group - teen girls - had experienced an increase in the rate of NITSs, from 12% in the first survey to 17% in the second.
Some form of NITS is permanent, and some is temporary, Henderson noted. "It's impossible to tell."
Some results not surprising
Henderson said she was not surprised they didn't find higher rates of hearing loss now that more teens are listening to music through headphones. That's because high-frequency hearing loss, for instance, comes only after years of exposure to loud sounds, so it would be unlikely in teenagers.
Even NITSs could become more common as teenagers age, she added. "It's possible that teenagers, as they become young adults, will have even more hearing loss."
There are several things teens can do to protect their ears, Henderson recommended. For one, they should always wear earplugs at loud concerts, buy environmental noise-cancelling headphones, and keep the volume down. "A general rule of thumb is you should be able to hear someone talking to you even if you have your earphones on."
Dr Peter Rabinowitz of Yale University in New Haven, who reviewed the findings, agreed that the increase in hearing loss among girls is probably a result of exposures to loud sounds. "That pattern (of hearing loss) is pretty characteristic of noise-induced hearing loss," he said.
But whether or not high volume from portable music players is to blame remains unclear, Rabinowitz added. More teens are listening to loud music, but most types of hearing loss didn't increase, and boys were no more likely to have NITSs as they were in the previous survey.
"This study does not totally prove that loud music is causing hearing damage in kids," he said.
But any diagnosis of hearing loss in teens is concerning, Rabinowitz noted. "We should be doing something to prevent it."
(Reuters Health, Alison McCook, December 2010)