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September 01, 2014

New Test to Identify People at Risk of Permanent Hearing Loss from Loud Noises

In any industrialized country like the United States, everybody has been exposed to loud noises whether from a lawnmower, playing in a band, shooting guns, or going to a rock concert. It also seems that some people compared to others appear more prone to temporary hearing loss after such loud noise exposure. You know... it's the ringing, fullness, and hearing loss after leaving the loud noise event. And than over a few hours or days, the hearing comes back to normal.

This temporary hearing loss after a loud noise event is called temporary threshold shift (TTS). Genetics play a factor in how resistant an individual is to TTS. Repetitive TTS also leads to permanent noise-induced hearing loss which is why there are rules for hearing protection for workers regularly exposed to loud noises. See charts.

However, especially in industries where workers are exposed to loud noises (or children who constantly listens to music loudly), this leads to the main question of identifying exactly who is at risk for permanent noise-induced hearing loss as steps could be taken to ensure extra protection or monitoring.

That's where TTS itself can be used to identify such at-risk individuals.

Researchers at the University of Vienna have figured out that by deliberately exposing patients to a 200-500 Hz sound at 100 decibels for 20 minutes and than measuring the TTS at 4 kHz within 10 minutes after end of exposure (2.5 minutes), they can predict with some degree of accuracy those who will eventually suffer permanent hearing loss in the future with continued loud noise exposure.

Based on a study population of 311 steelworkers (including controls) using a TTS cut-off of 14dbHL, the test had an 82% sensitivity and 53% specificity for predicting permanent hearing loss due to repetitive loud noise exposure over time.

In other words, this TTS test was accurate 82 percent of the time identifying workers considered vulnerable to hearing loss who actually did lose hearing over the years. However, when predicting who was NOT likely to experience hearing loss, the TTS test was correct only 53 percent of the time.

This TTS test can be administered in any office who can currently perform hearing tests as the equipment is the same. (Our office can administer this test.)

Just be aware that the TTS test is performed by deliberately exposing to the ear a 100 decibel sound for 20 minutes. A 100 decibel sound is about the level of sound produced by a motorcycle standing 3 feet away. A typical rock concert occurs at about 115 decibels. Pain begins at about 125 decibels.

Lest people think this test may be illegal itself, OSHA does permit a worker to be exposed to 100 decibel sound for no more than 2 hours per day, so a 20 minute long exposure is "legal" from that perspective.

Also, this test is not covered by insurance at this time given its novelty.

Reference:
Early prognosis of noise-induced hearing loss. Occup Environ Med doi:10.1136/oemed-2014-102200
Fauquier blog
Fauquier ENT

Dr. Christopher Chang is a private practice otolaryngology, head & neck surgeon specializing in the treatment of problems related to the ear, nose, and throat. Located in Warrenton, VA about 45 minutes west of Washington DC, he also provides inhalant allergy testing/treatment, hearing tests, and dispenses hearing aids. Google+ Christopher Chang, MD Bio

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