Untangling the genomics of noise-induced hearing loss and tinnitus: Contributions of Mus musculus and Homo sapiens

Association of polymorphisms in the catalase gene with the susceptibility to noise-induced hearing loss: A meta-analysis

OBJECTIVES

The association between single nucleotide polymorphisms (SNPs) of the Catalase (CAT) gene and noise-induced hearing loss (NIHL) has been reported in several case-control studies. However, their conclusions are conflicting. This study aimed to determine the association between CAT genetic variants and NIHL susceptibility.

METHODS

We searched PubMed, Embase, CNKI, Wanfang, and Web of Science for eligible English and Chinese studies published up to September 26, 2021. Studies reporting primary data that assessed the association between CAT SNPs and NIHL susceptibility were included. The quality of the included studies was assessed using the Newcastle-Ottawa Scale (NOS). The odds ratio (OR), 95 % confidence interval (CI), and P value were calculated to assess the strength of the association. Publication bias was explored using funnel plots and Egger's test.

RESULTS

Our meta-analysis included six articles involving 1428 patients and 2162 healthy controls. For rs208679, a significant association was detected in the allele model (A vs. G: OR = 0.81 [95 % CI, 0.67-0.97], P = 0.02) and the dominant model (AA vs. GG + AG: OR = 0.78 [95 % CI, 0.62-0.98], P = 0.03), but not in the heterozygote model, homozygote model, or the recessive model. For rs769217, rs7943316, and rs769214, no significant association was found in any genetic model. No significant publication bias was observed.

CONCLUSIONS

The rs208679 may be used in the Chinese population as a risk predictor for NIHL. While the rs769217, rs7943316, and rs769214 polymorphisms were not found to be associated with susceptibility to NIHL. Further studies with a larger population and higher quality are required to update the results.

The Interrelationship of Tinnitus and Hearing Loss Secondary to Age, Noise Exposure, and Traumatic Brain Injury

OBJECTIVE

Tinnitus has been the No. 1 disability at the Veteran Administration for the last 15 years, yet its interaction with hearing loss secondary to etiologies such as age, noise trauma, and traumatic brain injuries remains poorly characterized. Our objective was to analyze hearing loss and tinnitus, including audiogram data, of the Million Veteran Program within the context of military exposures in an aging population.

DESIGN

Health records, questionnaires, audiograms, and military data were aggregated for 758,005 Veteran participants in the Million Veteran Program 2011 to 2020, with relative risks (RR) calculated for ancestries, sex, hearing loss and military exposures such as combat, blast, and military era served. A multivariate model with significant demographic measures and exposures was then analyzed. Next, audiogram data stratified by sex were compared for those with and without tinnitus by two methods: first, mean thresholds at standard frequencies were compared to thresholds adjusted per ISO 7029:2000E age and sex formulae. Second, levels for those ≤40 years of age were compared with those 41 and older. Finally, a proportional hazards model was examined to ascertain the timing between the onset of tinnitus and hearing loss, calculated separately for electronic health record diagnoses (ICD) and self-report.

RESULTS

Tinnitus was either self-reported, diagnosed, or both in 37.5% (95% CI, 37.4 to 37.6), mean age 61.5 (95% CI, 61.4 to 61.5), range 18 to 112 years. Those with hearing loss were 4.15 times (95% CI, 4.12 to 4.15) as likely to have tinnitus. Americans of African descent were less likely to manifest tinnitus (RR 0.61, 95% CI, 0.60 to 0.61), as were women (RR 0.65, 95% CI, 0.64 to 0.65). A multivariate model indicated a higher RR of 1.73 for traumatic brain injury (95% CI, 1.71 to 1.73) and daily combat noise exposure (1.17, 95% CI, 1.14 to 1.17) than age (0.998, 95% CI, 0.997 to 0.998). Subjects ≤40 years of age had small but significantly elevated hearing thresholds through all standard frequencies compared to Veterans without tinnitus, and the effect of tinnitus on hearing thresholds diminished with age. In the hazard model, those >40 with new onset of tinnitus were at risk for hearing loss sooner and with greater incidence than those who were younger. The rate of hearing loss following tinnitus approached 100%. In contrast, only approximately 50% of those who self-reported hearing loss initially were at risk for later hearing loss, in contrast to ICD comparison, where those with ICD of hearing loss were more likely to sustain an ICD of tinnitus subsequently.

CONCLUSIONS

Evidence suggests that the occurrence of tinnitus in the military is more closely related to environmental exposures than to aging. The finding that tinnitus affects hearing frequencies across the audiogram spectrum suggests an acoustic injury independent of tonotopicity. Particularly for males >40, tinnitus may be a harbinger of audiologic damage predictive of later hearing loss.

The efficacy of acoustic therapy versus oral medication for chronic tinnitus: A meta-analysis

PURPOSE

To compare the efficacy of acoustic therapy (AT) and drug therapy (DT) for chronic tinnitus.

METHODS

We searched Pubmed, ScienceDirect, Chinese Journal Full-text Database (CNKI), Wanfang Database, Chinese Biomedical Literature Database (CBM), Embase, and Cochrane Library from the establishment of the database to December 2019. Meta-analysis was performed on the Tinnitus Handicap Inventory (THI) score and Visual Analogue Scale (VAS) with included literature using Revman 5.3 software.

RESULTS

A total of 18 documents were included, including 16 Chinese documents and 2 English documents, with 1774 patients (including 962 patients treated with AT and 812 patients treated with DT). The effect of AT (by the number of cases or ears) is better than that of DT (P < 0.05). After treatment, the THI value of AT was more evident than that of DT (WMD = -4.25, (-13.24, -5.29)). And the VAS value of AT was significantly lower than that of DT (WMD = -0.73, (-1.31, -0.15)).

CONCLUSION

Compared with DT, AT can significantly improve the efficacy of tinnitus and reduce the symptoms of tinnitus patients. Clinically, it can vigorously promote the application value of treating tinnitus by sound.

Noise-induced hearing loss and its prevention: Integration of data from animal models and human clinical trials

Animal models have been used to gain insight into the risk of noise-induced hearing loss (NIHL) and its potential prevention using investigational new drug agents. A number of compounds have yielded benefit in pre-clinical (animal) models. However, the acute traumatic injury models commonly used in pre-clinical testing are fundamentally different from the chronic and repeated exposures experienced by many human populations. Diverse populations that are potentially at risk and could be considered for enrollment in clinical studies include service members, workers exposed to occupational noise, musicians and other performing artists, and children and young adults exposed to non-occupational (including recreational) noise. Both animal models and clinical populations were discussed in this special issue, followed by discussion of individual variation in vulnerability to NIHL. In this final contribution, study design considerations for NIHL otoprotection in pre-clinical and clinical testing are integrated and broadly discussed with evidence-based guidance offered where possible, drawing on the contributions to this special issue as well as other existing literature. The overarching goals of this final paper are to (1) review and summarize key information across contributions and (2) synthesize information to facilitate successful translation of otoprotective drugs from animal models into human application.

Noise-induced hearing loss: Translating risk from animal models to real-world environments

Noise-induced hearing loss (NIHL) is a common injury for service members and civilians. Effective prevention of NIHL with drug agents would reduce the prevalence of NIHL. There are a host of challenges in translation of investigational new drug agents from animals into human clinical testing, however. Initial articles in this special issue describe common pre-clinical (animal) testing paradigms used to assess potential otoprotective drug agents and design-related factors that impact translation of promising agents into human clinical trials. Additional articles describe populations in which NIHL has a high incidence and factors that affect individual vulnerability. While otoprotective drugs will ultimately be developed for use by specific noise-exposed populations, there has been little effort to develop pre-clinical (animal) models that accurately model exposure hazards across diverse human populations. To facilitate advances in the translational framework for NIHL otoprotection in pre-clinical and clinical testing, the overarching goals of the current series are to (1) review the animal models that have been used, highlighting the relevance to the human populations of interest, (2) provide insight into the populations for whom pharmaceutical interventions might, or might not, be appropriate, and (3) highlight the factors that drive the significant individual variability observed in humans.