Evaluation of vestibular system with vHIT in industrial workers with noise-induced hearing loss

Role of Video Head Impulse Test to Assess Noise Exposure

Noise exposure has been reported to exert numerous detrimental effects on the human population, although most research has centred around hearing damage. Vestibular and balance loss have been demonstrated among industrial workers, although reports on this are still scarce. Vestibular loss increases the risk of falls, especially among industrial workers who are at constant risk. Nonetheless, the ideal investigation tool to investigate vestibular function remains unknown. We aim to review the available literature to elucidate the effect of noise exposure on semicircular canals using a video head impulse test (vHIT). A literature search identified only three studies involving 137 patients (mean age: 44.4). Semicircular canal deficit was found in 50.4% of the included participants, with lateral canal predominantly affected (71%). We highlight the importance of assessing the effect of noise exposure on vestibular function, especially among those prone to occupation-related vestibular loss.

Prevalence of Hearing Loss and Perceptions of Hearing Health and Protection among Florida Firefighters

Firefighters are exposed to extensive hazardous noise while on the job, both during routine tasks at the station and when responding to calls. However, little is known about firefighters' occupational noise hazards. This study employed mixed methods, including focus groups, a survey, and audiometric testing, to identify sources of noise in the firefighters' work environment, determine hearing protective strategies, discern firefighters' perceptions of occupational noise exposure and impacts to their health, and quantify the prevalence of hearing loss among South Florida firefighters. A total of 6 senior officers served in an expert panel, 12 participated in focus groups, 300 completed the survey, and 214 received audiometric tests. Most firefighters were unaware of the risk and their departments' policies, and did not participate in hearing protection practices and avoided using hearing protection devices, which they believed impede team communication and situational awareness. Nearly 30% of participating firefighters showed mild to profound hearing loss, a prevalence that is considerably worse than expected by normal aging alone. Educating firefighters about noise-induced hearing loss early in their careers may have significant health implications for their future. These findings provide insights for developing technologies and programs to mitigate the effects of noise exposure in the firefighting population.

Effects of noise on the vestibular system of normal-hearing workers

BACKGROUND: Studies in noise-exposed animals have shown changes in vestibular structures. Likewise, studies in humans have been suggesting that noise can damage the vestibular system, even with normal assessment results. OBJECTIVE: To assess the vestibular system of workers exposed to noise and to compare with individuals not exposed. METHODS: Twenty normal-hearing male adults were divided in the study group (SG), exposed to occupational noise, and control group (CG). We conducted the following procedures: medical history, Dizziness Handicap Inventory (DHI), Dix-Hallpike maneuver, and electronystagmography (eye and caloric tests). RESULTS: The DHI score did not differ between groups. The Dix-Hallpike maneuver was normal for both groups. All individuals had normal responses in the eye tests. 50% of the SG had hyperreflexia in the caloric tests, with a significant difference between the groups. There was a trend towards a statistical significance in the absolute values of angular speed of the slow component in the cold-air test, which were higher in the SG. There was a significant difference between the groups in the relative values of labyrinthine preponderance, which were higher in the SG. CONCLUSION: Our findings showed that 70% of the workers exposed to occupational noise had vestibular alterations identified with electronystagmography, whereas 100% of the individuals in the CG had normal results in the vestibular assessment. Moreover, only 20% of the sample in both groups had vestibular complaints, indicating the presence of subclinical vestibular changes in 50% of the individuals exposed to occupational noise.

Fall-related Injuries Mediate the Relationship between Self-Reported Hearing Loss and Mortality in Middle-Aged and Older Adults

BACKGROUND

Hearing loss is associated with a greater risk of death in older adults. This relationship has been attributed to an increased risk of injury, particularly due to falling, in individuals with hearing loss. However, the link between hearing loss and mortality across the lifespan is less clear.

METHODS

We used structural equation modeling and mediation analysis to investigate the relationship between hearing loss, falling, injury, and mortality across the adult lifespan in public-use data from the National Health Interview Survey and the National Death Index. We examined 1) the association between self-reported hearing problems and later mortality, 2) the associations between self-reported hearing problems and the risk of injury and degree and type of injury, 3) the mediating role of falling and injury in the association between self-reported hearing problems and mortality, and 4) whether these relationships differ in young (18-39), middle-aged (40-59) and older (60+) age groups.

RESULTS

In all three age ranges, those reporting hearing problems were more likely to fall, were more likely to sustain an injury, and were more likely to sustain a serious injury, than those not reporting hearing problems. While there was no significant association between hearing loss and mortality in the youngest category, there was for middle-aged and older participants and for both fall-related injury was a significant mediator in this relationship.

CONCLUSIONS

Fall-related injury mediates the relationship between hearing loss and mortality for middle-aged as well as older adults, suggesting a need for further research into mechanisms and remediation.

Effects of Noise Exposure on the Vestibular System: A Systematic Review

Despite our understanding of the impact of noise-induced damage to the auditory system, much less is known about the impact of noise exposure on the vestibular system. In this article, we review the anatomical, physiological, and functional evidence for noise-induced damage to peripheral and central vestibular structures. Morphological studies in several animal models have demonstrated cellular damage throughout the peripheral vestibular system and particularly in the otolith organs; however, there is a paucity of data on the effect of noise exposure on human vestibular end organs. Physiological studies have corroborated morphological studies by demonstrating disruption across vestibular pathways with otolith-mediated pathways impacted more than semicircular canal-mediated pathways. Similar to the temporary threshold shifts observed in the auditory system, physiological studies in animals have suggested a capacity for recovery following noise-induced vestibular damage. Human studies have demonstrated that diminished sacculo-collic responses are related to the severity of noise-induced hearing loss, and dose-dependent vestibular deficits following noise exposure have been corroborated in animal models. Further work is needed to better understand the physiological and functional consequences of noise-induced vestibular impairment in animals and humans.

Dual-task performance and vestibular functions in individuals with noise induced hearing loss

PURPOSE

The aim of this study was to evaluate the vestibular functions and dual-task performances of individuals with noise induced hearing loss.

MATERIALS AND METHODS

Fifty individuals with noise induced hearing loss and 25 healthy individuals were included in the study. Individuals with noise induced hearing loss were divided into 2 groups according to the pure tone average. Twenty-five patients with bilateral pure tone average between 20 dB HL and 40 dB HL were included in group I and 25 patients with bilateral pure tone average higher than 40 dB HL were included in group II. One-leg standing test, functional reach test, timed-up and go test, head impulse test, head shaking test, spontaneous nystagmus test and caloric test were carried out to evaluate the vestibular systems of all individuals. Visual analog scale was used to evaluate the imbalance intensity of individuals. In order to evaluate the dual-task performances of the individuals, individuals were given cognitive and motor tasks simultaneously with timed up and go test.

RESULTS

Individuals in group II had more abnormal caloric responses than the control group and individuals in group I. Also, individuals with higher hearing loss exhibited worse performance than other groups in eyes-closed one-leg standing test and dual-task situations.

CONCLUSION

Individuals with higher hearing loss (>40 dB) had more abnormal vestibular test results and worse dual-task performance than other groups. Vestibular evaluation and dual-task performance evaluation of factory workers with noise induced hearing loss can provide useful information to determine the risk of falling and fall prevention strategies in these individuals.

Intense noise exposure alters peripheral vestibular structures and physiology

The otolith organs play a critical role in detecting linear acceleration and gravity to control posture and balance. Some afferents that innervate these structures can be activated by sound and are at risk for noise overstimulation. A previous report demonstrated that noise exposure can abolish vestibular short-latency evoked potential (VsEP) responses and damage calyceal terminals. However, the stimuli that were used to elicit responses were weaker than those established in previous studies and may have been insufficient to elicit VsEP responses in noise-exposed animals. The goal of this study was to determine the effect of an established noise exposure paradigm on VsEP responses using large head-jerk stimuli to determine if noise induces a stimulus threshold shift and/or if large head-jerks are capable of evoking VsEP responses in noise-exposed rats. An additional goal is to relate these measurements to the number of calyceal terminals and hair cells present in noise-exposed vs. non-noise-exposed tissue. Exposure to intense continuous noise significantly reduced VsEP responses to large stimuli and abolished VsEP responses to small stimuli. This finding confirms that while measurable VsEP responses can be elicited from noise-lesioned rat sacculi, larger head-jerk stimuli are required, suggesting a shift in the minimum stimulus necessary to evoke the VsEP. Additionally, a reduction in labeled calyx-only afferent terminals was observed without a concomitant reduction in the overall number of calyces or hair cells. This finding supports a critical role of calretinin-expressing calyceal-only afferents in the generation of a VsEP response.NEW & NOTEWORTHY This study identifies a change in the minimum stimulus necessary to evoke vestibular short-latency evoked potential (VsEP) responses after noise-induced damage to the vestibular periphery and reduced numbers of calretinin-labeled calyx-only afferent terminals in the striolar region of the sacculus. These data suggest that a single intense noise exposure may impact synaptic function in calyx-only terminals in the striolar region of the sacculus. Reduced calretinin immunolabeling may provide insight into the mechanism underlying noise-induced changes in VsEP responses.

Effect of vibration on the vestibular system in noisy and noise-free environments in heavy industry

Background: Chronic exposure to whole body vibration can affect the gastrointestinal system, the lumbar spine, the peripheral veins and the vestibulocochlear system. Aims/Objectives: The aim of this study was to evaluate the effects of vibration on the vestibular system in noisy and noise-free environments using the video head impulse test (vHIT). Material and Methods: A total of 138 employees were included in this study. Group 1 were exposed to vibration and noise. Group 2 only exposed to vibration, with no exposure to noise. Group 3 were not exposed to noise or vibration. Results: Canal deficit was observed in 41 of 84 participants in Group 1, 7 of 24 participants in Group 2, and 1 of 30 participants in Group 3. There were more canal deficits in Group 1 and Group 2, than in Group 3 (p < .05). There was no significant difference between Group 1 and Group 2 in terms of canal deficits (p > 0.05). Conclusions and Significance: Semicircular canal deficit can be seen with the synergistic effect of noise and vibration.