A new analysis from a nationally representative health interview and examination survey found that nearly one in four (24 percent) of U.S. adults aged 20 to 69 years has features of his or her hearing test in one or both ears that suggest noise-induced hearing loss (NIHL). These findings, from the 2011-2012 National Health and Nutrition Examination Survey (NHANES), were published February 7 by the Centers for Disease Control and Prevention (CDC) in the CDC’s Vital Signs report. The research was conducted by the CDC with support from the National Institute on Deafness and Other Communication Disorders (NIDCD), part of the National Institutes of Health (NIH).
A person with NIHL may find it hard to understand speech in noisy environments, such as restaurants. Although there is no gold standard for measuring hearing loss from noise, NIHL is suggested by hearing loss in selected high frequencies (3, 4, and 6 kHz), with better hearing at lower frequencies, such as 500 and 1000 Hz, and at the higher frequency of 8 kHz. The results of a hearing test appear as a dip on an audiogram (a chart that shows how well a person can hear), which researchers refer to as an audiometric notch, or the ‘noise’ notch. The study used the audiometric notches as evidence suggesting noise-induced hearing loss. These audiometric notches affect a person’s ability to hear certain high frequencies, such as the high-pitched soft speech sounds of “t,” “f,” and “s,” which correspond with frequencies of 3, 4, and 6 kHz, respectively.
“Of the 24 percent of adults with an audiometric notch suggestive of noise-induced hearing loss, 6 percent had a notch in both ears, and 18 percent had a notch in only one ear,” said Howard J. Hoffman, M.A., a coauthor on the paper and director of the NIDCD’s Epidemiology and Statistics Program. “When hearing loss is found in both ears, the presence of the audiometric notch is more closely correlated with loud noise exposure than when the notch is found in only one ear. However, notches may be caused by noise and a variety of other factors.”
The report suggests that at least 10 million (6 percent) of adults in the U.S. under age 70—and perhaps as many as 40 million adults (24 percent)—may have NIHL based on evidence of noise notches in their hearing test results.
The researchers found that those who reported on-the-job exposure to loud or very loud noise were about twice as likely to have a noise notch in one or both ears as participants who reported not being exposed to loud or very loud noise in the workplace. Loud noise was defined as needing to speak in a raised voice, and very loud noise was defined as needing to shout to be understood by someone standing three feet away. One in three (33 percent) adults aged 20 to 69 years who reported exposure to loud or very loud noise at work had a noise notch. One in five (20 percent) of adults who did not report on-the-job exposure also had a noise notch in one (unilateral) or both ears (bilateral).
“We also found that 19 percent of young adults aged 20 to 29 had either unilateral or bilateral audiometric notches, with 4 percent having noise notches in both ears,” said Hoffman. “This finding reinforces the fact that young people also need to be aware of the risk of hearing loss from loud noise. Combined with other findings from the study, it’s clear that people of all ages need to be mindful of noise all around them, including in their leisure activities and home, and not just at work.”
Prolonged exposure to noise above 85 decibels (about the loudness of a lawnmower), can cause gradual hearing loss, while exposure to explosive noise can cause immediate hearing loss. Avoiding or limiting exposure to loud noise in the workplace, at home, and in the community may prevent or delay high-frequency hearing loss.
“Damage from loud noises often builds over time,” said NIDCD Director James F. Battey, Jr., M.D., Ph.D. “That’s why we encourage people to lower the volume, move away from excessive noise, and when you can’t do that, wear earplugs or other hearing protectors.”
To increase awareness about hearing loss from noise, the NIDCD has a national public education campaign, It’s a Noisy Planet. Protect Their Hearing.® Since 2008, Noisy Planet has educated children aged 8 to 12, their parents, and other educators about how to prevent noise-induced hearing loss.
The NIDCD and CDC authors published the Vital Signs report in part in response to recommendations from Hearing Health Care for Adults: Priorities for Improving Access and Affordability, a report published in June 2016 from the National Academies of Sciences, Engineering, and Medicine. Cosponsored by the National Institutes of Health (through the NIDCD and the National Institute on Aging), the CDC, other federal agencies, and a nonprofit patient advocacy group, the report calls for government agencies to strengthen efforts to collect, analyze, and disseminate data on hearing loss.
In December 2016, researchers reported in JAMA Otolaryngology that the overall prevalence of hearing loss in the 2011-2012 NHANES study period was 14 percent, a slight drop from 16 percent from the 1999-2004 NHANES data. This analysis did not examine audiometric notches. In the December JAMA paper, the researchers defined “speech-frequency” hearing loss as an average hearing threshold across four speech frequencies (0.5, 1, 2, and 4 kHz) that was greater than 25 decibels in loudness. In the current Vital Signs study, the researchers defined an audiometric notch as evidence of noise-induced hearing loss as a threshold difference of 15 decibels or greater at the high frequencies of 3, 4, and 6 kHz compared to the average threshold at the frequencies of 0.5 and 1 kHz and the threshold at 8 kHz was at least 5 decibels lower (better) than the maximum threshold at 3, 4, or 6 kHz. For more statistics on hearing and hearing loss, see the NIDCD's Quick Statistics about Hearing webpage.
To learn how noise can cause hearing loss, see the NIDCD fact sheet Noise-Induced Hearing Loss. For more information about measuring hearing loss, see the NIDCD’s What the Numbers Mean: An Epidemiological Perspective on Hearing webpage.