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NOISE-INDUCED HEARING LOSS IN TEENAGERS
Robert S. Schlauch
Department of Speech-Language-Hearing Sciences University of Minnesota Minneapolis, MN 55455
Introduction
The present author was invited to write the following article for Acoustics Today as a result of a memo he had sent to Thomas Rossing, the Editor of ECHOES, in regard to a recently published item. The Summer 2013 issue (Vol. 23, No. 3) of ECHOES carried the following news item (page 7) in its section titled “Acoustics in the News:”
“Noise, not age, is the leading cause
of hearing loss, an article in the
March 26 issue of the New York
Times reminds us. Tens of millions
of Americans, including 12 to 15
percent of school-age children,
already have permanent hearing
loss caused by everyday noise that we take for grant- ed. After poor service, noise is the commonest com- plaint about restaurants. Yet many proprietors believe that their customers spend more on food and drink in bustling eateries and do little to minimize sound levels. A survey by the American Speech-Language- Hearing Association found that 35 percent of adults and up to 59 percent of teenages reported listening to portable music devices at loud volumes. Some toys meant for young children, such as talking dolls, vehi- cles with horns, rubber squeaky toys, and musical instruments generate ear-damaging levels of noise.”
The cited article in the New York Times is available online at the site http://well.blogs.nytimes.com/2013/03/25/what-causes- hearing-loss/
It has the title “What causes hearing loss,” and is authored by Jane E. Brody, who is the personal health colum- nist for the Times. (She has been called the “high priestess of health” by Time Magazine.) The article carries the provoca- tive statement, “Tens of millions of Americans, including 12 to 15 percent of school-age children, already have permanent hearing loss caused by everyday noise that we take for grant- ed,” that was included in the ECHOES piece cited above, but the Times article does not include any explicit source for the stated statistic.
Such statements are not unusual in the popular litera- ture, and it may well be that the percentage range, 12 to 15 percents, is a commonly accepted premise regarding teen-age hearing loss.
Research that the author and his colleagues have report- ed over the past few years has shown that this percentage range, 12 to 15, is highly inflated, and seeing this in the news
(again) motivated the present author to write this article for Acoustics Today.
Possible sources of the 12 to 15 percent assertion
The NY Times article did not list a citation for the high prevalence of school-aged children’s noise-induced hearing loss (NIHL), but the likely source is one of two published analyses of National Health and Nutrition Examination Survey (NHANES) data (Niskar et al., 2001; Shargorodsky et al., 2010). NHANES data are collected peri- odically from a representative sample of adults and children throughout the United States to provide health statistics
and an understanding of the risk factors that contribute to diseases and health conditions. Hearing is one of the condi- tions assessed in these surveys. NHANES data are stored online and can be accessed by researchers. Table 1 summa- rizes the findings of several analyses of NHANES data from children along with their methods, controls, and findings. Subsequent sections of this article will expand on the content of this table to reveal what is known about NIHL in school- aged children.
Studies that reported a high prevalence of NIHL in school-aged children
Niskar et al. (2001) analyzed NHANES children’s data col- lected between 1988-1994 (http://www.cdc.gov/nchs/ nhanes/nh3data.htm) for notched hearing loss configurations, a loss often seen in persons with NIHL caused by workplace exposure. In early NIHL, hearing loss usually is seen first for frequencies between 3 kHz and 6 kHz. Even though most sounds that cause NIHL are broadband, the ear canal and con- cha can boost the level of high frequency sounds at the eardrum by more than 20 dB relative to that for other frequencies: this makes regions of the cochlea that code frequencies between 3 and 6 kHz more susceptible to damage. Niskar et al. selected criteria for defining a notched audiogram that required reduced thresholds at 3, 4 or 6 kHz and better thresholds for lower fre- quencies and for 8 kHz. Figure 1shows a typical notched audio- gram that exceeds Niskar et al.’s criteria for a hearing loss con- figuration they labeled as a noise-induced threshold shift (NITS). The author and his colleagues prefer the term high- frequency notched (HFN) audiogram rather than NITS because these notched audiograms have other causes, including genetic hearing loss and measurement variability. Their analy-
14 Acoustics Today, October 2013
“Pure-tone audiometry is the gold standard for quantifying hearing loss, but it is limited in its precision when identifying a small change in hearing or a mild hearing loss caused by incipient noise- induced hearing loss.”