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Nov. 15, 2011 -- One in five Americans aged 12 and older has hearing loss that interferes with their ability to communicate, according to new research.
"It's a pretty shocking number," says study researcher Frank R. Lin, MD, PhD, of Johns Hopkins University. The one in five, or about 48 million, have hearing loss in one or both ears.?
Lin also found that one in eight people aged 12 and older have hearing loss in both ears. That's about 30 million people.
Previous estimates have been lower, finding about 21 million to 29 million people with hearing loss, Lin says. His research is published in the Archives of Internal Medicine.
In another study, researchers found that college students, especially men and minorities, often turn up the volume on personal audio devices to hazardous levels.
"They tend to turn it up in noisy environments and then are surprised later at how loud it is," says study researcher Pamela A. Smith, PhD, assistant professor of audiology and speech pathology at Bloomsburg University. She is due to present the findings this week at the American Speech Language Hearing Association annual meeting in San Diego.
The good news, she says, is that people given information about these noise hazards tend to listen.
Previous estimates of hearing loss have been calculated from self-reported studies or from samples that do not represent the entire population, Lin says. He is an assistant professor of otolaryngology and epidemiology at Johns Hopkins.
To get a more accurate number, he analyzed data from the 2001-2008 cycles of the National Health and Nutritional Examination Surveys (NHANES). The data included results of hearing tests given to some participants.
Lin used criteria developed by the World Health Organization to define hearing loss. It was defined as a loss if it began to impair communication in daily life.
With every decade of age, hearing loss nearly doubles, Lin found. Women and blacks are less likely at any age to be affected. Lin is not sure why.
"Hearing loss as a whole is caused by a lot of different things," he tells WebMD. Genetics and aging are major factors. "Noise-induced hearing loss plays a role," he says.
People have different sensitivities to the effects of noise, he says.
In her survey of 384 college students, Smith found that 92% used a personal listening device.
Men and non-whites were more likely to set the devices at high volumes of 75% to 100% of maximum. They were especially likely to turn up the volume when in noisy backgrounds.
However, few students reported symptoms of hearing loss. These include, for instance, difficulty hearing speech when in a crowd.
More than three-quarters said they listen with ear-bud headphones. Those who use them tend to listen at higher volumes, other research shows.