The influence of tinnitus and hearing loss on the functional status of military Service members and Veterans

Therapeutic Function of Liraglutide for Mitigation of Blast-Induced Hearing Damage: An Initial Investigation in Animal Model of Chinchilla

INTRODUCTION

Auditory injuries induced by repeated exposures to blasts reduce the operational performance capability and the life quality of military personnel. The treatment for blast-induced progressive hearing damage is lacking. We have recently investigated the therapeutic function of liraglutide, a glucagon-like peptide-1 receptor agonist, to mitigate blast-induced hearing damage in the animal model of chinchilla, under different blast intensities, wearing earplugs (EPs) or not during blasts, and drug-treatment plan. The goal of this study was to investigate the therapeutical function of liraglutide by comparing the results obtained under different conditions.

MATERIALS AND METHODS

Previous studies on chinchillas from two under-blast ear conditions (EP/open), two blast plans (G1: 6 blasts at 3-5 psi or G2:3 blasts at 15-25 psi), and three treatment plans (blast control, pre-blast drug treatment, and post-blast drug treatment) were summarized. The auditory brainstem response (ABR), distortion product otoacoustic emission (DPOAE), and middle latency response (MLR) recorded within 14 days after the blasts were used. Statistical analysis was performed to evaluate the effect of liraglutide under different conditions.

RESULTS

ABR threshold shifts indicated that the conditions of the EP and open ears were substantially different. Results from EP chinchillas indicated that the pre-blast treatment reduced the acute ABR threshold elevation on the day of blasts, and the significance of such an effect increased with the blast level. Liraglutide-treated open chinchillas showed lower ABR threshold shifts at the later stage of the experiment regardless of the blast levels. The DPOAE was less damaged after G2 blasts compared to G1 when pre-blast liraglutide was administrated. Lower post-blast MLR amplitudes were observed in the pre-blast treatment groups.

CONCLUSIONS

This study indicated that the liraglutide mitigated the blast-induced auditory injuries. In EP ears, the pre-blast administration of liraglutide reduced the severity of blast-induced acute damage in ears with EP protection, especially under G2. In animals with open ears, the effect of liraglutide on the restoration of hearing increased with time. The liraglutide potentially benefits post-blast hearing through multiple approaches with different mechanics.

Prevalence and predictors of problematic tinnitus

OBJECTIVE

To determine the prevalence and characteristics of problematic tinnitus in a representative United States (US) sample.

DESIGN

Cross-sectional study of the NHANES database from 2011-2012 and 2015-2016.

STUDY SAMPLE

8029 records were included for analysis.

RESULTS

The prevalence of any tinnitus was 16.32%. Only 1.38% reported tinnitus as a big problem or worse. Univariate analysis revealed a statistically significant relationship between tinnitus constancy and duration with severity, where more constant perception and longer duration was related to increased severity (p < 0.0001). Multivariable models showed a clear relationship of increased odds ratio (OR) of problematic tinnitus with constancy of tinnitus but not duration. Furthermore, multivariable models showed higher Body Mass Index (OR= 1.013, 95% CI: 0.99-1.03), sleep trouble (OR = 2.016, 95% CI: 1.52-2.66) and comorbidities (OR = 1.43, 95%CI: 1.06-1.94) were all associated with increased problematic tinnitus, but not non-problematic tinnitus.

CONCLUSIONS

Our study demonstrated that the prevalence of problematic tinnitus is much lower than the prevalence of any tinnitus. There was also a relationship between BMI, sleep trouble, other comorbidities and increased odds of problematic tinnitus. Tinnitus severity was significantly related to constancy of perception but had a less clear relationship to duration.

A proposed association between subjective nonpulsatile tinnitus and migraine

Objective

Tinnitus is defined as the perception of sound in the absence of an external source. We propose the hypothesis that migraine can cause exacerbation of tinnitus in some patients.

Methods

English literature from PubMed has been reviewed.

Results

Studies have reported a high prevalence of cochlear symptoms in patients with migraine headaches and up to 45% of tinnitus patients have been shown to concomitantly suffer from migraine. Both conditions are thought to stem from central nervous system disturbances, involving disruption of the auditory and trigeminal nerve pathways. One proposed mechanism of this association is the modulation of sound sensitivity by trigeminal nerve activation of the auditory cortex during migraine attacks, resulting in tinnitus fluctuation in some patients. Increased brain and inner ear vascular permeability resulting from trigeminal nerve inflammation, can also cause observed headache and auditory symptoms. Tinnitus and migraine also share a number of symptom triggers including stress, sleep disturbances, and dietary factors. These shared features may help explain promising results of migraine therapies for the treatment of tinnitus.

Conclusion

Given the complex association between tinnitus and migraine, further investigation is needed to identify the underlying mechanisms and determine the optimal treatment strategies for managing migraine-related tinnitus patients.