Noise-Induced Hearing Loss: What You Don't Know Can Hurt You
Hearing loss has long been thought to be an unpleasant but inevitable side effect of aging. And aging is indeed the most common cause of hearing loss. But within the past year, two reports from the Centers for Disease Control
and Prevention (CDC) have documented the startling degree to which noise—both in the workplace and elsewhere in our daily lives—contributes to hearing damage.
Findings published in the CDC’s Feb. 7, 2017 Morbidity and Mortality Weekly Report (MMWR) demonstrated that 23.5 percent of people aged 20-69 who reported having good or excellent hearing had some degree of hearing loss, as measured by the presence of an audiometric notch (either unilateral or bilateral). While people exposed to loud noises at work were twice as likely to have hearing loss—nearly one-third of them had either a bilateral or unilateral notch—19.9 percent of those studied who reported no exposure to loud or very loud noise at work also had some degree of hearing loss.
DAILY NOISE EXPOSURE
It’s important to note that this report was based on data from the 2011–2012 National Health and Nutrition Examination Survey (NHANES), said Anne Schuchat, MD, the CDC’s acting director. “The NHANES survey allows us to not only rely on people’s symptoms, or what they’re aware of, but on documented testing. It’s surprising that a sizeable population of young adults already had noise-induced hearing damage, and that they didn’t work in noisy workplaces. Our emphasis in the past has largely been on reducing worker exposure to noise, but community or home noises are probably causing a lot of damage that is not evident.”
Although the new study did not pinpoint where participants were getting their noise exposure, Schuchat cited some examples of common community sources of hearing damage such as:
* two hours of exposure to a leaf blower at 90 decibels can cause substantial hearing damage with repeated exposures over time;
* 14 minutes at a sporting event with a noise level of 100 decibels can cause damage with repeated exposure; and
* two minutes at a rock concert with levels of 110 decibels can cause damage, again with repeated exposure.
HEARING HEALTH AT WORK
The new CDC report comes less than a year after another CDC report, published in MMWR April 22, 2016, which assessed hearing impairment in the workplace. Investigators compared the prevalence of hearing impairment within nine U.S. industry sectors using the audiograms of 1,413,789 noise-exposed workers from CDC’s National Institute for Occupational Safety and Health (NIOSH) Occupational Hearing Loss Surveillance Project. They estimated six levels of hearing impairment and calculated the impact that this impairment had on a person’s quality of life as measured in annual disability-adjusted life years (DALYs).
Work-related hearing impairment was found in all of the job sectors examined, although some areas were at particularly high risk. The mining sector had the highest prevalence of workers with any impairment (17%) and with moderate or worse impairment (3%), followed by construction (any impairment = 16%, moderate or worse impairment = 3%), and manufacturing (14% and 2%). Public safety, which includes police protection, fire protection, corrections, and ambulance services, had the lowest prevalence of workers with any impairment (7%).
Across all industries, 2.53 healthy years were lost annually for every 1,000 noise-exposed workers—and most of this loss was traceable to mild hearing impairment, which accounted for 52 percent of all healthy years lost, while moderate impairment accounted for 27 percent.
The good news is that noise levels in business sectors like manufacturing do seem to be going down, said exposure scientist Richard Neitzel, PhD, associate chair of environmental health sciences at the University of Michigan School of Public Health. “But newer job sectors present a whole new set of unknowns when it comes to noise exposure. What about the barista who’s next to the coffee grinder all day? And musicians and performers are working with stronger and more powerful systems, creating levels of sound that weren’t possible 20 years ago. Meanwhile, people are carrying around devices they can listen to music on for 18 hours a day, right in their ears, at very high volume. It’s too early to know what the effects on hearing will be, but we need to err on the side of caution with this generation that is experiencing unprecedented exposures to noise.”
THE AUDIOLOGIST’S ROLE
“Since we don’t have a cure for hearing loss, we need to put an appropriate amount of attention toward prevention, both in the workplace and in the community setting,” said Brian Fligor, ScD, chief audiology officer at Lantos Technologies and former director of diagnostic audiology at Boston Children’s Hospital. “These are largely man-made disorders, and there should be man-made remedies for them. When it comes to noise-induced hearing loss, that ounce of prevention is worth way more than a pound of cure—which is really a pound of management, not a cure.”
The nation’s 14,000 audiologists should be taking a leading role in educating their patients and the public in general on the daily risks posed by noise exposure and on the precautions to avoid long-term overexposure and damage, said Fligor. “As hearing health professionals, we usually see people after there has already been some damage to their hearing. A patient will come to see us about, say, ringing in their ears, and we have to tell them that their ears are ringing because they have hearing loss that they didn’t know about. Our efforts need to be focused not just on helping them compensate for their hearing loss, but on preserving and protecting the hearing they have left. We also need to teach young people that hearing is valuable and precious, and can be taken away very easily.”
Audiologists should also be aware of the role played by noise exposure in “hidden hearing loss”—that is, hearing loss that causes problems for a person in everyday life, but that does not produce audiogram findings that are outside of normal limits. Animal-model research has suggested that the synapses between hair cells and cochlear nerve terminals may be the first to degenerate in noise-induced hearing loss (as well as hearing loss due to aging). While this neural degeneration may not manifest itself in testing, it can contribute to difficulty understanding speech, especially in noisy environments. The animal-model findings were backed up in humans by a 2016 study involving college students (PLoS One. 2016;11:e0162726 http://bit.ly/2gefP46). Students with a history of noise exposure had normal thresholds at standard audiometric frequencies, but significant threshold elevation at high frequencies (10-16 kHz), “consistent with early stages of noise damage,” the authors wrote. “The high-risk group also showed significantly poorer performance on word recognition in noise or with time compression and reverberation, and reported heightened reactions to sound consistent with hyperacusis.”
TOOLS FOR DETECTION PROTECTION
You can’t protect yourself against something you’re not aware of. With that in mind, multiple sound measurement apps for smartphones have been introduced to the market, designed to keep track of how much noise you’ve been exposed to, and for how long. Are any of them any good? Yes, according to a NIOSH study—but only a handful are.
In 2014, NIOSH investigators examined 192 sound measurement apps http://bit.ly/2ne3zCr on the iOS and Android platforms, and found only four iOS apps they deemed to have necessary features and functionalities and to be sufficiently accurate. (No Android apps made the cut.) Those four were the NoiSee, SoundMeter, SPLnFFT, and Noise Hunter apps. Of those, NIOSH ranked Sound Meter as the best: “The evidence suggests that for A-weighted data, SoundMeter is the app best suited for occupational and general purpose noise measurements,” they wrote.
And in January 2017, NIOSH released its own free Sound Level Meter app. When the user starts the app, it provides a readout of the sound level using the built-in microphone (or external microphone, which NIOSH reports is more accurate) and reports the sound level in A-, C-, or Z-weighted decibels. It also calculates the peak sound level during the recording time, time-weighted average, and percentage of the maximum allowable daily dose—with exposures of 100 percent and above considered hazardous. Users can save and share their measurement data, and if location services are enabled, the phone’s GPS feature can provide an exact location of the noise measurement.
SOUND STANDARDS FOR HEADPHONES
Although there are many possible sources for general daily noise exposure—leaf blowers, snow blowers, construction jackhammers (even for people who don’t work in construction, living near a building site can do nearly as much damage to the ears)—one of the most common sources is loud music. The growth of personal electronic devices over the past decade means that more people than ever are listening to music, often at high volume, through earbuds or headphones.
“The type of device a person is using when they listen to music or podcasts can make a big difference,” said Neitzel. “With cheap knockoff earbuds that are putting as much music out of the ear as into it, and not blocking the sound around the user, the person will have to turn that device up way too loud just to hear the music and overcome the background noise. A little extra money spent on sound-isolating or noise-blocking earbuds can make a huge difference.”
For musicians—not just those who play in a loud garage band, but kids in the local marching band as well—earplugs are equally important. “We need to advise our patients who are involved in music that investing in custom hearing protection is one of the greatest, easiest, least expensive things to do for their hearing health,” said Fligor. “Spending $150 to $200 for a pair of earplugs that should last a couple of years will significantly lessen the chances that your patient will wake up one morning and say, ‘Something’s really off.’ If that is too much for your patient’s budget, the Etymotic Research ER-20 high-fidelity earplugs don’t fit everyone perfectly, but they fit well enough and are much better than the cheap foamy earplugs, for less than $20.”
Noise-induced hearing loss starts early. An earlier study based on NHANES data found that 12.5 percent of 6-19-year-olds (6.8 million) and 16.8 percent of 12-19-year-olds (5 million) in the United States have documented evidence of elevated hearing thresholds directly attributable to noise exposure (Pediatrics. 2011;127:e39 http://bit.ly/2mNf1tu). In 2015, the World Health Organization (WHO) estimated that 1.1 billion teenagers and young adults worldwide are at risk for hearing loss, linked primarily to the unsafe use of personal audio devices and damaging levels of sound at concerts and other entertainment venues (Hearing Journal. 2016;69:20 http://bit.ly/2gKSLIX).
Even a child’s toys may be putting his or her hearing at risk. For about 10 years, Hamid Djalilian, MD, an otolaryngologist at the University of California-Irvine, has done annual testing of popular children’s toys to determine which ones have the highest sound levels. While none of the toys Djilalian has tested exceeds the 120 dB threshold that can cause hearing damage from a single exposure, many of them fall into the 85 dB-or-more category, in which hearing loss can result from repeated exposure. For example, the popular toddler toy from Leap Frog, “My Own Laptop,” has a maximum dB level of 110, and Disney Junior’s “Rockin’ Doc Singalong Boombox” hits a max of 105 dB.
Djalilian suggests home remedies that patients can use to protect their children or grandchildren’s hearing: Either put masking tape or super glue over the speaker to mute the sound, or put tape over the volume control to prevent the child from blasting the sound at unsafe levels.
Deanna Meinke, PhD, professor of audiology at the University of Northern Colorado and a specialist in noise-induced hearing loss in children, is co-director of Dangerous Decibels, a national educational initiative on noise-induced hearing loss. Its 50-minute program for K-12 classrooms uses scientific tools to help students learn how to measure sound, understand decibels, and make models of their own ear—and in the process, teaches them to safeguard their hearing by “Turning it Down,” “Walking Away,” and “Protecting Ears.”
“One great educational tool we have is our Jolene mannequin, built using an old fashion mannequin and a sound level meter wired to a silicon ear,” Meinke said. “We use her to measure the sound levels of personal audio systems. You can build your own Jolene—some audiologists have them in their practice, and their office staff have been taught to use them to teach people waiting for their appointments. Grandparents love learning about music players and taking what they’ve learned home for their children and grandchildren.”
“There are many opportunities for audiologists to educate their patients and their wider communities about noise-induced hearing loss, beyond the office,” said Meinke. “Use your social media accounts—Facebook, blogs, Twitter. Keep this issue in front of your patients and the public.”