October 14, 2016
3 min read

Cochlear synaptopathy linked to speech comprehension deficits in college students

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Cochlear synaptopathy, or hidden hearing loss, was associated with college students’ difficulty in comprehending speech in challenging auditory environments, according to recent study findings.

“While hearing sensitivity and the ability to understand speech in quiet environments were the same across all subjects, we saw reduced responses from the auditory nerve in participants exposed to noise on a regular basis and, as expected, that loss was matched with difficulties understanding speech in noisy and reverberating environments,” Stéphane F. Maison, PhD, a researcher in the Eaton-Peabody Laboratories at Massachusetts Eye and Ear and assistant professor of otolaryngology at Harvard Medical School, said in a press release.

Maison and colleagues have had success, under some conditions, with restoring sensory cells and the auditory nerve using growth factors in animal models.

To assess cochlear synaptopathy in humans, the investigators recruited 34 young adults, aged 18 to 41 years, from surrounding colleges and universities into an observational study and performed behavioral threshold audiometry, electrophysiology and word recognition tests to determine cochlear function and hearing. Participants were divided into groups at either low-risk (n = 12; mean age, 24 years) or high-risk (n = 22; mean age, 25 years) for ear damage based on self-reports of noise exposure levels and hearing protection use. All participants had unremarkable otoscopic examinations with audiometric thresholds from 0.25 to 8 kHz in both ears. All testing was conducted at the Northeastern University Speech-Language and Hearing Center in a sound-treated booth.

Data analysis presented significant deficits in difficult word-recognition tests within noisy environments in the high-risk group vs. the low-risk group. High-risk participants demonstrated significant threshold tolerance at all frequencies above 8 kHz that grew to about 20 dB HL at 16 kHz (intergroup differences, .01 < P < .001). In addition, students in the high-risk group exhibited changes in auditory potentials defined by symptoms of cochlear synaptopathy.

“Establishing a reliable diagnosis of hidden hearing loss is key to progress in understanding inner ear disease,” Maison said in the release. “Not only may this change the way patients are tested in clinic, but it also opens the door to new research, including understanding the mechanisms underlying a number of hearing impairments such as tinnitus and hyperacusis.” – by Kate Sherrer

Disclosure: The researchers report no relevant financial disclosures.