An observed relationship between vestibular function and auditory thresholds in aircraft-maintenance workers

Vestibular Hypersensitivity in Patients with Chronic Noise Exposure

It has been demonstrated that high-intensity noise exposure adversely affects the human balance function. The Tullio phenomenon (TP) refers to sound-induced imbalance which is resulted from hypersensitivity of vestibular end organs to normal acoustic stimuli. Although different etiologies have been attributed to TP, evidence on the role of excessive noise exposure in the development of this symptom is limited. The present study aims to assess the vestibular functions in patients manifesting TP symptom who were exposed to long-term excessive noise levels. This was an analytic cross-sectional study conducted on 17 males diagnosed with TP with a history of chronic noise-induced hearing loss (TP group) and 17 healthy individuals. All subjects in both groups underwent complete otological, videonystagmography (VNG), and cervical vestibular myogenic potential (cVEMP) assessments. The most common complaint in TP subjects was vertigo and imbalance. During the VNG assessment, we found abnormal positional nystagmus and caloric irrigation (vestibular hyperfunction) results in 4 (23.53%) and 9 (52.94%) patients, respectively. Seven (41.17%) patients indicated cVEMP thresholds which were abnormally lower than the normal values ( ≤ 70 dB HL). However, when both VNG and cVEMP results were considered together, the abnormal rate reached 70.58% (12 of 17 cases). Our findings showed that both the semicircular canal as well as otolith stuctures could be affected in TP patients with a history of chronic noise exposure.

[A cross-sectional study and risk factors analysis of tinnitus in flight support personnel of PLA air force]

Objective:The aim of this study is to understand the epidemiological characteristics of tinnitus among flight support personnel and analyze its audiological characteristics and related risk factors. Methods:The information of tinnitus was collected by a method of cross-sectional investigation using questionnaire survey and audiology test among the flight support personnel of two stations of PLA air force. Results:The incidence of tinnitus among 666 subjects included was 24.2%, the THI grade was mainly grade 1 and grade 2. There were differences in THI scores among groups with different working years, but only differences in tinnitus incidence among groups with different frequency of hearing loss. Multivariate logistic regression analysis showed that grade of high frequency hearing loss（OR=1.39）, conscious hearing loss（OR=1.79） and frequency of asking others to repeat words（OR=1.64） were independent risk factors of tinnitus. The incidence of HF-HL and EHF-HL in ears with tinnitus among 0-5 working years was higher than that without tinnitus, while the incidence of EHF-HL in ears with tinnitus was not different from that without tinnitus among 6-10 and >10 working years. There was moderate correlation between THI scores and SAS standard scores（r=0.759）, and weak correlation between THI scores and PSQI scores（r=0.445）. Conclusion:The risk of tinnitus in high-frequency hearing loss and recessive hearing loss is increased; working years can affect the severity of tinnitus, while hearing conditions at different frequencies only affect the incidence of tinnitus; with increasing age, noise exposure plays a role in the occurrence of tinnitus decreasing gradually.

Modulation of Auditory Perception Laterality under Anxiety and Depression Conditions

The objective of this work is to confirm the asymmetry in non-linguistic auditory perception, as well as the influence of anxiety-depressive disorders on it. Eighty-six people were recruited in the emotional well-being group, fifty-six in the anxiety group, fourteen in the depression group, and seventy-seven in the mixed group. In each group, audiograms were obtained from both ears and the differences were statistically analyzed. Differences in hearing sensitivity were found between both ears in the general population, such differences increased in people with anxiety-depressive disorders. When faced with anxiety-depressive disorders, the right ear suffered greater hearing loss than the left, showing peaks of hyper-hearing at the frequency of 4000 Hz in the anxiety subgroup, and hearing loss in the depression subgroup. In relation to anxiety, the appearance of the 4:8 pattern was observed in the right ear when the person had suffered acute stress in the 2 days prior to the audiometry, and in both ears if they had suffered stress in the 3–30 days before said stress. In conclusion, the advantage of the left ear in auditory perception was increased with these disorders, showing a hyperaudition peak in anxiety and a hearing loss in depression.

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.

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.

Vestibular short-latency evoked potential abolished by low-frequency noise exposure in rats

The vestibular system plays a critical role in detection of head movements and is essential for normal postural control. Because of their anatomical proximity to the cochlea, the otolith organs are selectively exposed to sound pressure and are at risk for noise overstimulation. Clinical reports suggest a link between noise exposure and balance problems, but the structural and physiological basis for this linkage is not well understood. The goal of this study was to determine the effects of low-frequency noise (LFN) on the otolith organs by correlating changes in vestibular short-latency evoked potentials (VsEPs) with changes in saccular afferent endings following noise exposure. LFN exposure transiently abolished the VsEP and reduced the number of stained calyces within the sacculus. Although some recovery of the VsEP waveform could be observed within 3 days after noise, at 3 wk recovery was only partial in most animals, consistent with a reduced number of afferents with calyceal endings. These data show that a single intense noise exposure is capable of causing a vestibular deficit that appears to mirror the synaptic deficit associated with hidden hearing loss after noise-induced cochlear injury. NEW & NOTEWORTHY This is the first study to explore the effects of low-frequency high-intensity noise on vestibular short-latency evoked potential (VsEP) responses, which shows a linkage between attenuated noise-induced VsEPs and pathological changes to otolith organ afferents. This finding suggests a potential limitation of the VsEP for evaluation of vestibular dysfunction, since the VsEP measurement may assess the activity of a specific class rather than all afferents.

A comparison of techniques to mitigate Simulator Adaptation Syndrome

We investigated the effectiveness of galvanic cutaneous stimulation (GCS) and auditory stimulation in mitigating simulator adaptation syndrome (SAS). Fifteen drivers (9 men; M age = 23.2 years) participated in a driving simulation experiment comparing three different stimulation conditions (GCS, auditory stimulation and no stimulation as a base line condition) in curves on a virtual urban circuit. GCS and auditory stimulation decreased SAS by reducing head sway. Both sources of stimulation can be recommended as countermeasures against SAS. We encourage the use of stimuli which influence the balancing ability to the design of future simulator protocols and devices to mitigate SAS.

PRACTITIONER SUMMARY

We have provided evidence on the effectiveness of two different stimuli as countermeasures against simulator adaptation syndrome (SAS). We concluded that the positive impact of body sway might play a role in SAS and therefore encourage the use of stimuli which influence the balancing ability to mitigate the symptoms of SAS.

Some health effects of aircraft noise with special reference to shift work

BACKGROUND

Aircraft noise is an environmental stressor. A positive relationship exists between noise and high blood pressure. Shift work is an additional hazardous working condition with negative effect on the behavior attitude of workers.

OBJECTIVE

This study aimed at investigating some health hazards for shift work on workers at Cairo International Airport (CIA), Egypt, as a strategic work place, with more than one stressor.

SUBJECTS AND METHODS

Assessment of noise effects were carried out in four working sites at the airport besides control sites. The average noise level in the exposure sites was 106.5 dB compared with 54 dB at the control sites. The study comprised a group of 200 male workers exposed to aircraft noise and 110 male workers not exposed to noise as control group. All workers had full general medical examination after filling specially formulated questionnaire. Hearing impairment, raised blood pressure, headaches, disturbed sleep, and symptoms of anxiety were more prominent among the exposed workers than the control. Symptoms of upper respiratory tract were reported among night shifters of both groups with high tendency for smoking. Thus, night-shift workers at CIA work under more than one stressor. Hypertension and smoking might act as intermediate factors on the causal pathway of complaints, making aircraft noise and night shift acting as two synergistic stressors. Airport workers are in need for aggressive hearing conservation programs. Organization of the working hours schedule is mandatory to avoid excessive noise exposure.

Falls Risk and Hospitalization among Retired Workers with Occupational Noise-Induced Hearing Loss

L’étude vise à vérifier si une perte auditive d’origine professionnelle, contribue au risque de chute avec hospitalisation chez des retraités. Des hommes (≥ 65 ans) exposés au bruit en moyenne durant 30,6 ans et dont la perte auditive bilatérale moyenne est de 42,2 dB HL (3, 4 et 6 kHz) sont étudiés. 72 travailleurs retraités hospitalisés suite à une chute sont appariés à 216 retraités des mêmes secteurs industriels. Des modèles de régression logistique conditionnelle sont utilisés pour estimer le rapport de cote (RC) par catégories de perte auditive. Les résultats montrent une relation entre une perte auditive sévère (≥ 52,5 dB HL) et une chute (RC = 1,97 IC95%: 1,001 à 3,876). Réduire les chutes chez les personnes âgées favorise le maintien de leur autonomie. Il faut développer les connaissances sur les effets nocifs du bruit au travail, promouvoir la santé auditive et favoriser de saines conditions de travail.