Does a 10 dB Hearing Loss Really Matter?
“Normal” hearing at any frequency in humans is defined as the ability to perceive a sound at a volume of 20 dB or less. Hearing loss is not considered to be “severe” until the volume required to perceive a sound reaches a threshold of 70 dB, and “profound” hearing loss (or deafness) occurs when the sound must be 100 dB or more in volume to be heard. Given these ranges of hearing and the corresponding degrees of hearing loss, it is reasonable to ask if a 10 dB hearing loss is actually significant. For example, if a person with normal hearing at baseline is exposed to a stimulus that is harmful to the ears (such as loud music or an ototoxic substance) and that person’s hearing is 10 dB worse as a result, does this matter, considering that he or she is still far from being deaf?
There is good reason to conclude that a 10 dB hearing loss is indeed significant. Because the decibel scale is logarithmic, a 10 dB reduction in hearing means that a sound would need to be 10-times more intense to evoke the same perception as before the hearing loss. This would likely make a significant difference in an individual’s ability to accurately perceive the clarity of speech that he or she is hearing, especially in a noisy environment (Campbell et al., 2016). The conclusion that a 10 dB hearing loss is clinically relevant is supported by workplace standards set by the Occupational Safety and Health Administration (OSHA). According to these standards, if a worker sustains a 10 dB reduction in hearing at three frequencies and has at least a mild hearing loss as a result of occupational noise exposure, a significant work related injury (WRI) has occurred. Such a WRI must be reported, and is used to monitor hazardous work areas. The Department of Defense has adopted an identical standard for defense-related work environments (Campbell et al., 2016).
Because a 10 dB hearing loss is significant, it can be concluded that a 10 dB improvement in hearing is clinically meaningful as well. This should be encouraging to developers of treatments for hearing improvement. Sponsors of preclinical and clinical efficacy trials of otic treatments might assume that a 10 dB improvement relative to controls is too small to matter, and that only improvements of 20 dB or more are promising. In reality, a 10 dB improvement in hearing could generate great enthusiasm among clinicians, scientists, and investors. A trial at St. Jude Children’s Research Hospital in Tennessee serves as an example. A team of scientists screened more than 4,000 small molecules as protectors against cisplatin-induced hearing loss, and the most successful molecule (kenpaullone, a CDK2 inhibitor) minimized hearing loss by 10 dB (Teitz et al., 2018). Significant excitement was generated, including an article in MedicalNewsToday announcing that a “new drug ‘could save the hearing of millions’” (Railton, 2018).
References Campbell, K., Hammill, T., Hoffer, M., Kil, J., & Le Prell, C. (2016). Guidelines for auditory threshold measurement for significant threshold shift. Otol Neurotol 37, e263-e270.
Railton, D. (2018). New drug ‘could save the hearing of millions’, in MedicalNewsToday (https://www.medicalnewstoday.com/articles/321143.php).
Teitz T., Fang, J., Goktug, A.N., Bonga, J.D., Diao, S., Hazlitt, R.A., et al. (2018). CDK2 inhibitors as candidate therapeutics for cisplatin- and noise-induced hearing loss. J Exp Med 215(4), 1187- 1203.
Authors David Hicks, M.D.: Dr. Hicks directs business development at Turner Scientific, and has significant training and experience in clinical treatment of ear disorders. Contact: firstname.lastname@example.org
Jeremy Turner, Ph.D.: Dr. Turner is the founder and Chief Scientific Officer at Turner Scientific. He completed his Ph.D. in auditory neuroscience, and has more than 22 years’ experience in preclinical hearing loss, tinnitus, and ototoxicity research. Contact: email@example.com