The efficacy of N-acetylcysteine to protect the human cochlea from subclinical hearing loss caused by impulse noise: A controlled trial

Abstract

In military outdoor shooting training, with safety measures enforced, the risk of a permanent, noise-induced hearing loss is very small. But urban warfare training performed indoors, with reflections from walls, might increase the risk. A question is whether antioxidants can reduce the negative effects of noise on human hearing as it does on research animals. Hearing tests were performed on a control group of 23 military officers before and after a shooting session in a bunker-like room. The experiments were repeated on another group of 11 officers with peroral adminstration of N-acetyl-cysteine (NAC), directly after the shooting. The measurements performed were tone thresholds; transient-evoked otoacoustic emissions, with and without contralateral noise; and psycho-acoustical modulation transfer function (PMTF), thresholds for brief tones in modulated noise. Effects from shooting on hearing thresholds were small, but threshold behavior supports use of NAC treatment. On the PMTF, shooting without NAC gave strong effects. Those effects were like those from continuous noise, which means that strict safety measures should be enforced. The most striking finding was that the non-linearity of the cochlea, that was strongly reduced in the group without NAC, as manifested by the PMTF-results, was practically unchanged in the NAC-group throughout the study. NAC treatment directly after shooting in a bunkerlike room seems to give some protection of the cochlea.

Tinnitus and Other Auditory Problems – Occupational Noise Exposure below Risk Limits May Cause Inner Ear Dysfunction

“…Very few subjects with fully developed hyper-PMTFs (P-type = 3), suggesting exposure to impulse noise possibly associated to damage in the inner hair cell area [4], [16], [22], were found in this study. Although the Industry group had more self-reported impulse noise incidents (p<0.01) than the other groups, this did not result in significantly more hyper-PMTFs than in the other groups.…”

Associations between dietary quality, noise, and hearing: Data from the National Health and Nutrition Examination Survey, 1999–2002

“…Thus, it is perhaps not that surprising that otoprotection studies using impulse noise in animals have been promising (Cassandro et al, 2003; Hight et al, 2003; Kopke et al, 2005; Coleman et al, 2007; Bielefeld et al, 2011; Gavriel et al, 2011; Xiong et al, 2013). Human trials assessing otoprotection after impulse noise have suffered from a variety of shortcomings including the lack of a placebo control against which recovery could be compared (Suckfuell et al, 2007) and variable changes in hearing in real-world trials, with TTS not consistently detected even in control subjects (Le Prell et al, 2011c; Lindblad et al, 2011). Variability has been a challenge in laboratory studies as well (Spankovich et al, 2013).…”

Efficacy and safety of N-acetylcysteine in prevention of noise induced hearing loss: A randomized clinical trial

“…In a double-blind crossover study, human males received NAC (1200 mg/day) or placebo for 14 days. This study showed that NAC may prevent noise-induced TTS among occupationally noiseexposed men (Lin et al, 2010) (Lindblad et al, 2011). The NAC treatment consisted of acetylcysteine, 200 mg, (Tika).…”