by Daniel Fink, MD
On December 16, 2016, an article appeared in the New York Times, Americans’ Hearing Loss Decreases Even With Ubiquitous Headphones, which focused on a study by Howard J. Hoffman, MA, et al. (Hoffman) that appeared in the respected medical journal JAMA Otolaryngology–Head & Neck Surgery. The study found that there was a declining prevalence of hearing loss in U.S. adults. The results were considered surprising, as the study showed that the rate of hearing loss in adults age 20-69 had decreased from 15.9% to 14.1%. The researchers, epidemiologists, and statisticians at the National Institute for Deafness and Other Communication Disorders, who conducted the study, are among the best in the world, and the data came from the Centers for Disease Control and Prevention’s well-respected National Health and Nutrition Surgery.
The results were considered surprising because two other recent federal reports, one in October 2015 from the President’s Council of Advisors on Science and Technology (PCAST) and the other in June 2016 from the National Academy of Science’s Institute of Medicine (IOM) (since renamed the Health and Medicine Division), emphasized that hearing loss, especially in older Americans, was a major national problem. Both of these reports cited an analysis by Frank Lin, MD PhD, Johns Hopkins University, that showed that 48 million Americans suffered significant hearing loss, with the prevalence increasing sharply with age.
I am personally involved in the question of what the facts are, since in an editorial in the January 2017 issue of the American Journal of Public Health I write about the inappropriate use of the 85 decibel occupational noise exposure standard, which should not be applied to the general public, citing Lin’s research and other studies that show increased hearing loss in young people age 12-19.
So, what do the data really show?
I am not an epidemiology expert like Mr. Hoffman and his distinguished co-authors. Their methods appear sound, their data sources as good as one can find in the epidemiology of hearing loss. The first caveat is that this study, as with all studies of the epidemiology of hearing loss in the pubic, is based on survey methodology. A group of 3831 participants are the study population, from which conclusions about the entire U.S. population were drawn. It would be too costly to test hearing in millions of people.
The second caveat is that there are newer techniques, currently only used in research and not yet in clinical use, demonstrating that before hearing loss can be detected by standard hearing tests (called pure tone audiometry), a phenomenon dubbed “hidden hearing loss” may have taken place. Hidden hearing loss has been found in young people and older adults. So while Hoffman’s study is encouraging, it may not be able to completely report what is really happening with Americans’ hearing.
The third point–not a caveat–is that Hoffman et al. studied adults age 20-69 and did not include young people under age 20. Those under age 20 may be the group most at risk of hearing loss due to ubiquitous use of personal music players at loud volumes. Two studies, using lower thresholds for measuring hearing loss than Hoffman et al. or Lin et al. used, found high levels of subclinical hearing loss (hearing loss greater than 15 decibels but less than 25 decibels) in young Americans. One from 1998 found that 15% of young people had measurable hearing loss, and the other from 2010 showed an increase in the prevalence of hearing loss to almost 20%. This is worrisome because studies of auditory acuity in young people traditionally found excellent hearing.
The fourth point also isn’t a caveat, but a quote from the last line of Hoffman’s abstract: “Despite the benefit of delayed onset of HI (hearing impairment), hearing health care needs will increase as the US population grows and ages.”
It’s great news that the percentage of Americans age 20-69 with hearing loss (the epidemiology term for this is “prevalence”) has decreased from 15.9% to 14.1%. But that still means that there are millions of Americans with hearing loss–and that’s too many! Further, subclinical hearing loss appears to be increasing in young Americans, and, as the Hoffman study notes, hearing loss in older Americans is a significant health problem.
Finally, a point of contention: noise exposure is a major cause of hearing loss, and not aging as is implied in the study. Why would men have nearly twice as much hearing impairment (18.6%) as women (9.6%)? Is it an effect of testosterone levels on the auditory system, in which case one might actually expect hearing to improve as men get older, or is it the result of more noise exposure from work and recreational activities in men than women? Noise and hearing loss are still major problems in the U.S. and in the world, and the non-auditory effects of noise on health, which are coming into greater focus, continue unabated.
So yes, the prevalence of hearing loss in American adults may be declining, but when Lin’s analysis showed that approximately 25% of adults in their 60s, 33% of adults in their 70s, and half of those over age 80 have significant hearing loss–data cited in the PCAST and IOM Committee reports–it is obvious that there is still a major problem and still much to be done to prevent noise-induced hearing loss here and abroad.
And I and others have said before, but it bears repeating: noise-induced hearing loss is 100% preventable. If people avoid noise exposure and protect their ears from noise, they should be able to preserve natural hearing well into old age, rather than needing to rely on assistive hearing devices. The only evidence-based safe noise level remains a 70-decibel time-weighted average for a 24-hour period.
Dr. Fink is a leading noise activist based in the Los Angeles area. He serves on the board of the American Tinnitus Association, is the interim chair of Quiet Communities’s Health Advisory Council, and the founding chair of The Quiet Coalition, an organization of science, health, and legal professionals concerned about the impacts of noise on health, environment, learning, productivity, and quality of life in America.