Effects of oral zinc supplementation on patients with noise-induced hearing loss associated tinnitus: A clinical trial

Abstract

Background Zinc plays a vital antioxidant role in human metabolism. Recent studies have demonstrated a correlation between noise-induced hearing loss (NIHL) and oxidative injury; however, no investigation has focused specifically on the subgroup of NIHL associated tinnitus patients. We aimed to evaluate the effectiveness of zinc supplementation in treating NIHL associated tinnitus. Methods Twenty patients with tinnitus and a typical NIHL audiogram (38 ears) were included in this study. Another 20 healthy subjects were used as the control group. A full medical history assessment was performed, and each subject underwent an otoscopic examination, basic audiologic evaluation, distortion product otoacoustic emissions (DPOAEs), tinnitus-match testing, Tinnitus Handicap Inventory (THI) and serum zinc level analyses. After 2 months of treatment with zinc, all tests were repeated. Results There was a significant difference between pretreatment and post-treatment within the tinnitus group (73.6 vs. 84.6 μg/dl). The pre- and post-treatment difference in serum zinc was significantly higher in the young group (≦50 years) compared to the old group (19.4 ± 11.4 vs. 2.6 ± 9.2 μg/dl, respectively; p = 0.002). There were no statistically significant differences in hearing thresholds, speech reception thresholds, or tinnitus frequency and loudness results before and after treatment. In addition, 17 patients (85%) showed statistically significant improvement of THI-total scores post-treatment, from 38.3 to 30 ( p = 0.024). Conclusions Zinc oral supplementation elevated serum zinc levels, especially in younger patients. THI scores improved significantly following zinc treatment in patients with NIHL associated tinnitus. However, no improvements in objective hearing parameters were observed.

Kaempferol and zinc gluconate mitigate neurobehavioral deficits and oxidative stress induced by noise exposure in Wistar rats

“…This result is also in harmony with previous reports that zinc plays a principal function in the maintenance of the integrity of Cu-Zinc SOD as a co-factor and also in regulating glutathione, which is crucial in cellular antioxidant defence mechanisms [57]. Yeh et al [4] also reported the mitigating effect of oral zinc supplementation on patients with noise-induced hearing loss associated tinnitus. Furthermore, zinc stabilises the thiol pool by protecting the sulfhydryl group, hence it shields from oxidation [58].…”

“…Documented reports show that zinc deficiency exacerbates the generation of ROS while its supplementation limits the formation of free radicals in rats [28]. Similarly, in young adults, increased levels of free radicals have been linked with impaired neurobehavioural performance, however, this impairment improves notably upon supplementation with zinc [4,29]. As such, this study aimed to evaluate the mitigative effects of kaempferol and zinc gluconate on noise-induced neurobehavioral impairments and oxidative stress in Wistar rats.…”

“…Sustained exposure to sound levels greater than 85 dB, or sudden exposure to impulse noise lead to irreversible damage of sensory structures including the cochlea [13], and modifies the morphology of astrocytes [14]. Once damaged, the sensory hair cells in the cochlea do not regenerate, and ultimately results in permanent loss of hearing [2,4]. Foregoing reports have shown that mice and rats exposed to high-noise intensity respond by freezing into a still stance, while exposure of rats to 95 dB at 0.5-5 kHz for a period of 5 minutes per day for 28 weeks, alters behavior and induces aggression.…”

Auditory Neural Plasticity in Tinnitus Mechanisms and Management

“…Zinc is a structural component of superoxide dismutase which is the primary line of defense against oxidative stress. A significant improvement in the THI score was achieved in noise-induced hearing loss-associated tinnitus patients treated by zinc [ 152 ], while another study showed an adverse result in elderly tinnitus patients [ 153 ]. In any case, a Cochrane review concluded that there is no evidence of efficacy of oral zinc supplementation in adults with tinnitus [ 154 ].…”

Evergreen influenza – Tackling an old enemy with fresh munitions

“…Therefore, Yeh et al. investigate here the effectiveness of zinc supplementation in a subgroup of noise-induced hearing loss patients suffering additionally from tinnitus [21] . They conclude that although there were no improvements in objective hearing parameters, 85% of patients showed amelioration in a subjective evaluation of life quality restriction due to the tinnitus.…”