“Teenagers really underestimate how much noise they are exposed to,” Dr. Josef Shargorodsky of Brigham and Women’s Hospital in Boston told Reuters Health.
“Often the individual won’t notice it, but even slight hearing loss may lead to differences in language development and learning,” said Shargorodsky, who led the new research.
The study, published in the Journal of the American Medical Association, compared national surveys from the early 1990s and the mid-2000s. Each included only a few thousand adolescents, but was carefully designed to represent the whole country.
In the first survey, about 15 percent of teenagers had some degree of hearing loss, as measured by trained staff. Some 15 years later, that number had risen by a third, to nearly 20 percent.
“That’s a few kids per classroom who will have hearing problems,” said Shargorodsky.
Most of the hearing loss was in one ear only. While it was usually slight, one in 20 adolescents had more pronounced problems -- up 50 percent since the first survey.
“This certainly is big news,” said Alison Grimes, who manages the audiology clinic at Ronald Reagan-UCLA Medical Center in Los Angeles. “It has some potential implications in terms of children’s learning.”
Hearing loss is very common in the elderly, Grimes said, but she added that it was concerning to see it creep into the younger age brackets.
In babies and young children, hearing problems are known to delay language development, which in turn influences performance in other areas. Slight hearing loss, for instance, makes it difficult to distinguish between high-frequency consonants like “s” and “f.”
The science is less clear for adolescents, but it is easy to imagine how being hard of hearing could hamper learning, said Grimes, past president of the American Academy of Audiology.
“What is the primary job of a kid or teenager? It is to sit in a classroom and listen to a teacher lecturing,” she told Reuters Health. “We know from a lot of data that noisy classrooms are one of the biggest challenges to learning.”
Grimes often puts hearing aids on children with slight to mild impairments, although the decision depends on how much the child’s life is being affected.
Shargorodsky said he was surprised by the new findings. Better medical care for ear infections -- one of the usual suspects in hearing damage -- should in theory have decreased the numbers, he said.
The reasons for the rise are still murky. When asked about noise exposure -- on the job, from firearms or recreational activities, for instance -- the teenagers didn’t indicate any change.
But Shargorodsky said that might not necessarily be true. “We knew from before that it is difficult to ask this age group about noise exposure -- they underestimate it.”
Few people would call it noise when they listen to music on their MP3 player, for instance.
“There is a difference between what we consider to be loud and what is physically intense and could be hazardous to the ear,” said Grimes. Although it’s not clear that these devices are to blame, Grimes said it was still a good idea to turn down the volume and take frequent breaks from listening.
But, having been the mother of two teenagers, she pointed out the advice would likely fall on deaf ears. She said the American Academy of Audiology had also contacted Steve Jobs, the CEO of Apple, about adding a volume limiter on iPods. But they never heard back.
For now, said Shargorodsky, “it is important to try to learn why there has been this increase in hearing problems.”
SOURCE: link.reuters.com/nyz95m JAMA/Journal of the American Medical Association, August 18, 2010.
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