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Do You Have Hidden Hearing Loss?

Long exposure to even low-level noise may cause this underdiagnosed disorder

Ear exam

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You're dining out with friends in a busy restaurant and listening as they talk about … well, you're not entirely sure; you're struggling to make out what the heck they're saying. Strange, because your hearing is usually pretty sharp and you aced a recent audiogram. So what's behind all the static?

It could be hidden hearing loss, also called hidden hearing disorder, a term used to describe a specific hearing problem in which you can hear just fine in quiet or normal settings but have difficulty when there's competing background noise. Tough environments include crowded restaurants, cocktail parties and bustling workplaces.

Experts say many people have this disorder (which can coexist with tinnitus and hypersensitivity to sound) and don't know it.

"It may be hard to hear in restaurants, but they're probably not sufficiently motivated to see an audiologist,” says Daniel B. Polley, director of the Lauer Tinnitus Research Center at Massachusetts Eye and Ear and an associate professor of otolaryngology head and neck surgery at Harvard Medical School. And even if sufferers are motivated to do so, this condition can't always be detected in the quiet testing room for an audiogram — the gold-standard test of hearing sensitivity.

As part of research conducted at Massachusetts Eye and Ear, study authors reviewed more than 100,000 patient records over 16 years and found that about 1 in 10 who visited the audiology clinic had complaints of hearing difficulty; yet auditory testing revealed they had normal audiograms.

Causes

A big part of the problem is that life's become too loud, and it's affecting our hearing. “There are more people; there are more mechanized devices; there's more background noise,” Polley says. “Our longevity and the amount of noise in the environment have combined to create this perfect storm of difficulty.”

And it doesn't take much to inflict damage. In fact, says Catherine Palmer, audiology program director in the University of Pittsburgh's School of Health and Rehabilitation Sciences and president of the American Academy of Audiology, “most researchers feel that long exposures to even low-level noise may cause hidden hearing loss."

What's going on in our ears — and in our brain

Hidden hearing disorder occurs when the connections between the hair cells in the inner ear and the nerves that carry hearing signals to the brain are lost, so information can't be transmitted. (In other words, the brain is getting an incomplete signal.) Standard hearing tests can't detect these changes that hinder our ability to hear in louder settings. In fact, you can lose nearly 90 percent of the electrical connections before a doctor is able to see an irregularity.

But that may not be the whole story. When it comes to hidden hearing loss, some researchers believe that we should shift our attention away from our ears and toward our brain.

"There is a widespread misconception that the ear and the auditory nerve synapses hold all the answers about why we struggle with hearing as we age,” Polley observes. “This is not the case. The brain creates the perception of sound, and measures of the brain function will be able to predict hidden hearing disorders more accurately than measures of the ear, because the brain is the arbiter of sound perception, even if the problem begins in the ear.”

To that end, Polley and his colleagues at Massachusetts Eye and Ear have been working to “find a biomarker for hidden hearing disorder, so that we can focus on the neurological cause for the complaint.”


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Diagnosing hidden hearing loss

Though standard pure-tone audiograms may not be able to detect hidden hearing disorder, a trip to an audiologist is a good idea if you are having any trouble hearing. “The vast majority of individuals who have this kind of hearing difficulty don't have hidden hearing loss,” says Christopher Spankovich, an associate professor at the University of Mississippi Medical Center School of Medicine in the department of otolaryngology and communicative sciences. “Rather, they most likely have some mild degree of hearing loss and would benefit from some sort of mild-gain amplification,” he notes, referring to devices that offer low-level amplification for people with minimal hearing loss.

The symptoms of hidden hearing loss and mild hearing loss are very similar, Spankovich says: difficulty understanding speech in noisy environments, trouble following conversations and ringing or buzzing in the ears. “The only way an individual who has perceived hearing deficit will know if they have hidden hearing loss is if they see an audiologist to have a comprehensive audiological evaluation.”

Tests that can demonstrate evidence of hearing damage include an extended high-frequency pure-tone audiogram; an otoacoustic emissions (OAE) test, which examines how well your inner ear is functioning by measuring otoacoustic emissions (sounds the inner ear emits when responding to another sound, which can show early-stage damage); and speech-in-noise tests, designed to simulate real-life conditions.

Curious about how well you'd do? Take an online test devised for the Associated Press in conjunction with the Mailman Center for Child Development at the University of Miami. How it works: You'll be asked to repeat a series of simple sentences. The exercise kicks off in a quiet atmosphere but slowly introduces background noise, which gradually increases with each phrase.

Living with the disorder

There's no cure for hidden hearing disorder, but there are communication strategies — and even some nifty technologies — that can reduce the impact of noise on listening and lessen further damage.

Shut it out. If you're going to be around loud sounds, protect your ears by wearing a noise-reducing device. “If you like to go to concerts and listen to loud music, consider getting musician earplugs,” Spankovich suggests. You can even get a custom-made pair. If you hunt or target-shoot, hearing protection is a must, to reduce your risk for further damage, so slip on a pair of noise-canceling earmuffs. And turn down the volume when listening to tunes using earbuds.

Try environmental manipulation. “We don't have holes behind our ears; we have them in front,” says Spankovich. “If you're trying to have a conversation in a noisy restaurant, put the noise to your back and put your dining companion in front of you, so you can visualize them and see their mouth and face. This will automatically improve the signal-to-noise ratio.” Another tip: When dining out, ask to be seated at a booth, to help block out surrounding noise, or try to socialize in quieter settings, Palmer recommends.

Turn to tech. Yep, there's an app for that. Consider using a directional microphone to capture sound and deliver it to your hearing device, to improve speech recognition in noise. Spankovich offers two. Live Listen allows you to turn the microphone on your iPhone into a table microphone that can wirelessly communicate to your hearing aid or Bluetooth-enabled earbuds. Ear Machine, created by scientists funded by the National Institute on Deafness and Other Communication Disorders from the National Institutes of Health, lets you use the microphone on your Smartphone to pick up sounds and amplifies those sounds to your earbuds.

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