Auditory Brainstem Response Altered in Humans With Noise Exposure Despite Normal Outer Hair Cell Function.

This was an observational comparison, not a treatment trial. It cannot show that noise exposure caused the smaller wave I amplitudes. The study did not examine cochlear synapses directly, so it cannot prove hidden hearing loss or synaptopathy in humans. Reduced wave I amplitude could also reflect inner hair cell, auditory nerve, or outer hair cell changes not captured by DPOAEs. Noise exposure history relied on interviews and questionnaires. Twelve non Veterans reported firearm use only on the questionnaire after enrollment, and 14 Veterans did not have usable questionnaire data for this study. The sample was small and sex balance was imperfect: the non Veteran control group skewed toward females and the Veteran High Noise group toward males. All participants had normal pure-tone thresholds and normal DPOAE screening, so the findings do not apply to people with obvious hearing loss or poor outer hair cell function. Testing was done in one ear, many months to years after exposure, and did not measure speech understanding in noise, tinnitus, or functional communication.

Do not conclude that this proves cochlear synaptopathy or that a small ABR wave I amplitude means a patient has hidden hearing loss. The study used an indirect measure, did not examine synapses, included only young people with normal audiograms and DPOAE screening, and could not rule out other causes of reduced wave I amplitude.