U. FLORIDA (US) — A small study with college students found that a quarter of those tested had hearing loss, and they didn’t even know it. Researchers suspect MP3 players and iPods may be partly to blame.
The college students involved assumed their hearing was normal, but tests showed 25 percent measured 15 decibels or more of hearing loss—not severe enough to require a hearing aid, but enough to disrupt learning. Seven percent measured a loss of 25 decibels or more, which is enough to be clinically diagnosed as having mild hearing loss.
“You would expect normal hearing in that population,” says Colleen Le Prell, associate professor of speech, language, and hearing sciences at the University of Florida. “The criteria for normal hearing we used for the study were, we thought, extremely liberal criteria.”
The findings are reported in the journal International Journal of Audiology.
The students who volunteered for the study were asked about their previous exposure to loud noise, such as playing a musical instrument, listening to personal music players, using lawn equipment, or attending sporting events or concerts. Participants then received hearing tests in a sound booth at all of the sound frequencies used in a traditional full clinical hearing test.
Hearing loss occurred in both the range of frequencies identified as “speech frequencies” because of their importance for speech discrimination, and higher frequencies of 6 and 8 kilohertz.
“With high frequency hearing loss a person can miss a lot of subtle speech sounds, making it much harder to discriminate different vowels or phonemes,” Le Prell says. “It would also be much harder to hear sounds like bird songs or children’s voices.”
The increased rates of hearing loss in young adults may be related to the popularity of personal music players. The study found the highest levels of high frequency hearing loss were in male students who reported using personal music players, but more research is needed with a larger sample size to determine the role of personal music players and gender in noise-induced hearing loss.
“Dr. Le Prell’s article is consistent with what we know of early noise-induced hearing loss: It’s insidious and more prevalent in young men than women,” says Brian Fligor, an instructor in otology and laryngology at Harvard University who was not involved in the study.
“Their sample size was fairly small, making it hard for the researchers to actually find something, but the fact they did shows the size of the effect is of both scientific and clinical significance.
“These small but measurable changes in hearing in this young adult population suggest that they will have communicatively important hearing deficits earlier, perhaps decades earlier, than they should, due to the premature wear and tear on their hearing system.”
More thorough hearing tests for school children and better hearing health education for children and adolescents, is needed, Le Prell says.
“When you look carefully at hearing loss at specific frequencies or higher frequencies than you would in a traditional school-based hearing test, you find a much, much higher rate of hearing screening failures,” she says.
“The implication is that the current screening protocols are potentially missing a lot of hearing loss, based on the kinds of failure rates that we’ve detected when you broaden the criteria.”
More sophisticated hearing screenings of school children, like those used in clinical tests, may help educators and parents intervene to improve a student’s listening ability, Le Prell says.
“A number of studies have shown that even a mild hearing loss that isn’t treated clinically is associated with behavioral issues in school, like poor performance on tests and lower evaluations by teachers.”
Researchers from the University of Michigan and Southern Illinois University contributed to the study.
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