Effect of antioxidant supplementation on the auditory threshold in sensorineural hearing loss: a meta-analysis

Introduction

Hearing loss is conceptualized as any impairment of the ability to hear and/or detect speech or environment sounds, regardless of cause, type, or degree. It may occur at different stages of life; during pregnancy or childbirth, in childhood, adulthood or old age. It should be noted that aging is the most common cause of sensorineural hearing loss followed by noise-induced hearing loss, and both are closely related to the formation of reactive oxygen species. Dietary antioxidant supplementation has been employed as a therapeutic strategy to prevent and/or delay the risks of major human diseases.

Objective

To assess randomized clinical trials to determine the effect of antioxidant supplementation on the auditory thresholds in patients of different age groups with sensorineural hearing loss.

Methods

This systematic review consisted of a search in the following databases: MEDLINE, CENTRAL, ScienceDirect, Scopus, Web of Science, LILACS, SciELO and ClinicalTrials.gov. Additionally, the gray literature was also searched. The search strategy included terms related to the intervention (antioxidant supplementation), primary outcome (sensorineural hearing loss), as well as terms related to randomized clinical trials to improve search sensitivity.

Results

Based on 977 potentially relevant records identified through the search in the databases, ten full-text publications were retrieved for further evaluation. The increase in threshold at the 4 kHz frequency was statistically higher in the control group (1.89 [1.01–2.78], p < 0.0001) when compared to the NAC group and the ginseng group, whereas at 6 kHz, the threshold increase was higher in the control group (1.42 [?1.14–3.97], p = 0.28), but no statistically significant differences were found between groups.

Conclusion

Ginseng was the antioxidant agent that showed the best effect in preventing auditory threshold worsening at the frequency of 4 kHz, but not at 6 kHz in patients with sensorineural hearing loss caused by exposure to high sound pressure levels. There was no improvement in the thresholds with vitamin E supplementation.