Effect of N-acetyl-cysteine in prevention of noise-induced hearing loss: a systematic review and meta-analysis of randomized controlled trials

Introduction: Noise-induced hearing loss is one of the most prevalent causes of hearing impairment and occupational diseases. Although multiple factors lead to noise-induced hearing loss, prevention and protection strategies remain limited. Studies in the past decade have employed antioxidants, especially N-acetyl-cysteine, to prevent noise-induced hearing loss. Therefore, this systematic review and meta-analysis of randomized controlled trials evaluated the effect of N-acetyl-cysteine on the prevention of noise-induced hearing loss. Material and methods: This systematic review and meta-analysis included relevant studies from the Cochrane Library, EMBASE, PubMed, ScienceDirect, Scopus, and Web of Science by using related terms. The study only included randomized controlled trials in meta-analyses and assessed the quality of the identified randomized controlled trials by using the Cochrane Risk of Bias tool. Two authors extracted and calculated data on characteristics and hearing threshold. The results are presented as weighted mean difference (WMD) with 95% confidence interval (CI). Results: This study identified five randomized controlled trials that randomized 1,115 patients into N-acetyl-cysteine and control groups. The meta-analysis evidenced that N-acetyl-cysteine has greater protective effects against hearing threshold shifts than the control in the 0 to 4 kHz (WMD = –3.39, 95% CI: –6.56 to –0.22) and 0 to 6 kHz (MD = –3.49, 95% CI: –6.57 to –0.41) subgroups. Conclusions: The present review and meta-analysis recommends that N-acetyl-cysteine may be considered as an option for protective therapy for noise-induced hearing loss. Nonetheless, larger randomized controlled trials are requisite for further investigation and verification.