Nearly one in five American teens, some 6.5 million youngsters, suffered from hearing loss in 2006, a rise of around 30 percent from 12 years earlier, new research showed Tuesday.
Published in the Journal of the American Medical Association, the study found that in the majority of cases the hearing loss was slight, girls were less likely to have it than boys, and that it was more common in teens living below the poverty line.
But the spike among young Americans took researchers aback, especially as more kids in 2006 were vaccinated against illnesses that could cause hearing loss and awareness of music-induced cases had risen.
"What surprises us a little bit is the difference between the previous time that this data was gathered and the most recent," said Josef Shargorodsky of Brigham and Women's Hospital, the lead author of the study.
"There was a 30-percent increase in prevalence of any hearing loss in this age group and there was a much greater, about 50 percent increase, in the prevalence of mild or worse hearing loss," he said.
Researchers led by Shargorodsky studied data from two sets of hearing tests performed on 1,771 12- to 19-year-olds.
The first tests, conducted between 1988 and 1994, found nearly 15 percent of US teens had some hearing loss, while the second tests, between 2005 and 2006, found a 31-percent increase in the rate of teen hearing loss to 19.5 percent.
The researchers saw no difference in estimated noise exposure between the two periods in the study, but said a recent study of children with slight to mild hearing loss in Australia found that "reported use of personal stereo devices was associated with a 70 percent increased risk of hearing loss.
"The effects of noise exposure on hearing loss in adolescents deserve further study," they said, also calling for further studies to determine reasons for the spike in hearing-impaired US teens and identify risk factors that can be changed to prevent hearing loss.
Even slight hearing loss in school-aged children can "create a need for speech therapy, auditory training and special accommodations," the study says.
Children with mild hearing loss can develop impaired speech and language development, which can go on to affect their educational achievement and emotional development.