scholarly journals Exposure to Intense Noise Causes Vestibular Loss

2020 ◽  
Vol 185 (Supplement_1) ◽  
pp. 454-461
Author(s):  
Courtney E Stewart ◽  
Ariane C Kanicki ◽  
David S Bauer ◽  
Richard A Altschuler ◽  
W Michael King

ABSTRACT Introduction The vestibular system is essential for normal postural control and balance. Because of their proximity to the cochlea, the otolith organs are vulnerable to noise. We previously showed that head jerks that evoke vestibular nerve activity were no longer capable of inducing a response after noise overstimulation. The present study adds a greater range of jerk intensities to determine if the response was abolished or required more intense stimulation (threshold shift). Materials and Methods Vestibular short-latency evoked potential (VsEP) measurements were taken before noise exposure and compared to repeated measurements taken at specific time points for 28 days after noise exposure. Calretinin was used to identify changes in calyx-only afferents in the sacculus. Results Results showed that more intense jerk stimuli could generate a VsEP, although it was severely attenuated relative to prenoise values. When the VsEP was evaluated 4 weeks after noise exposure, partial recovery was observed. Conclusion These data suggest that noise overstimulation, such as can occur in the military, could introduce an increased risk of imbalance that should be evaluated before returning a subject to situations that require normal agility and motion. Moreover, although there is recovery with time, some dysfunction persists for extended periods.

2020 ◽  
Vol 123 (2) ◽  
pp. 658-669 ◽  
Author(s):  
C. E. Stewart ◽  
D. S. Bauer ◽  
A. C. Kanicki ◽  
R. A. Altschuler ◽  
W. M. King

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.


2018 ◽  
Vol 119 (2) ◽  
pp. 662-667 ◽  
Author(s):  
Courtney E. Stewart ◽  
Ariane C. Kanicki ◽  
Richard A. Altschuler ◽  
W. M. King

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.


Author(s):  
Courtney E Stewart ◽  
David Scott Bauer ◽  
Richard A Altschuler ◽  
William Michael King

Exposure to 120 decibel sound pressure level (dB SPL) band-limited noise results in delayed onset latency and reduced vestibular short-latency evoked potential (VsEP) responses. These changes are still present four weeks after noise overstimulation. Noise induced hearing loss (NIHL) has been shown to vary in extent and duration based on noise intensity. This study investigated whether noise-induced peripheral vestibular hypofunction (NPVH) would also decrease in extent and/or duration with less intense noise exposure. In the present study, rats were exposed to a less intense noise (110dB SPL), but for the same duration (6 hours) and frequency range (500-4000 Hz) as used in previous studies. The VsEP was assessed 1, 3, 7, 14, 21, and 28 days after noise exposure. In contrast to 120 dB SPL noise exposure, the 110 dB SPL noise exposures produced smaller deficits in VsEP responses that fully recovered in 62% of animals (13/21) within one week. These findings suggest that NPVH, a loss or attenuation of VsEP responses with a requirement for elevated stimulus intensity to elicit measurable responses, is similar to NIHL, i.e., lower sound levels produce a smaller or transient deficit. These results show it will be important to determine the extent and duration of vestibular hypofunction for different noise exposure conditions and their impact on balance.


2019 ◽  
Vol 166 (E) ◽  
pp. e53-e56
Author(s):  
Richard Ramsey ◽  
J Greenough ◽  
J Breeze

IntroductionHealth professionals working in the dental environment are potentially at risk of noise-induced hearing loss (NIHL) due to the use of clinical and laboratory equipment. Workplaces engaging in the practice of dentistry within the UK are subject to legislation from the Control of Noise at Work (CNW) regulations 2005. Clinicians working in the military are at further increased risk of NIHL due to exposure from additional risk factors such as rifles or aircraft engines. To our knowledge, no authors have previously studied the noise levels experienced in a military dental setting or compared noise levels in a typical dental practice with current UK legislation.MethodMeasurements of noise levels experienced by a dentist, dental nurse and dental hygienist during a standard conservation procedure were assessed using wearable noise dose-badges. Furthermore, noise levels within a dental technician’s work space were also assessed. Noise levels produced by representative clinical and laboratory equipment were assessed and compared with CNW legislation.ResultsThe highest level for clinical equipment was produced by the suction apparatus while aspirating up a cup of water at 76 dB. For laboratory equipment, the lower exposure action value (LEAV) of 80 dB would be exceeded in 2.1 hours’ use of the trimmer, 3.6 hours’ use of the vibrating table and 9 min use of the airline.ConclusionsNoise levels experienced by clinicians within the dental surgery were well below the legislative LEAV thresholds for both peak and continuous noise. However, noise levels produced by laboratory equipment were far higher and there is clearly the potential for excessive noise exposure for dental professional in the everyday setting. Dental professionals responsible for dental laboratory settings must be familiar with the CNW regulations and measures put in place that control the inadvertent breach of legislation. Hearing protection must be mandated when using equipment that exceeds the LEAV and an educational programme is required to explain both their correct use and the rationale behind it. Methods of mitigating that risk further require exploration such as alternative methods of completing the tasks performed by the airline or reducing the noise generated by it, such as by reducing the supply pressure or using an alternative nozzle design.


2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Afua A. Amoabeng Nti ◽  
Thomas G. Robins ◽  
John Arko Mensah ◽  
Duah Dwomoh ◽  
Lawrencia Kwarteng ◽  
...  

Abstract Background Informal electronic waste recycling activities are major contributors to ambient air pollution, yet studies assessing the effects or relationship between direct/continuous exposure of informal e-waste workers to particulate matter and cardiovascular function are rare. Methods Repeated measurements of fractions of PM2.5, PM10–2.5, and PM10 in personal air of informal e-waste workers, (n = 142) and a comparable group (n = 65) were taken over a period of 20 months (March 2017 to November, 2018). Concurrently, 5-min resting electrocardiogram was performed on each participant to assess resting heart rate variability indices. Linear mixed-effects models were used to assess the association between PM fractions and cardiac function. Results SDNN, RMSSD, LF, HF and LH/HF ratio were all associated with PM. Significant associations were observed for PM2.5 and Mean NN (p = 0.039), PM10 and SDNN (p = 0.035) and PM 10–2.5 and LH/HF (p = 0.039). A 10 μg/m3 increase in the concentrations of PM 2.5, PM10–2.5, and PM10 in personal air was associated with reduced HRV indices and increased resting HR. A 10 μg/m3 per interquartile (IQR) increase in PM10–2.5 and PM10, decreased SDNN by 11% [(95% CI: − 0.002- 0.000); (p = 0.187)] and 34% [(95% CI: − 0.002-0.001); (p = 0.035)] respectively. However, PM2.5 increased SDNN by 34% (95% CI: − 1.32-0.64); (p = 0.493). Also, 10 μg/m3 increase in PM2.5, PM10–2.5 and PM10 decreased RMSSD by 27% [(− 1.34–0.79); (p = 0.620)], 11% [(− 1.73, 0.95); (p = 0.846)] and 0.57% [(− 1.56–0.46); (p = 0.255%)]. Conclusion Informal e-waste workers are at increased risk of developing cardiovascular disease from cardiac autonomic dysfunction as seen in reduced HRV and increased heart rate.


2020 ◽  
Author(s):  
Pauline Barbeau ◽  
Alan Michaud ◽  
Candyce Hamel ◽  
Danielle Rice ◽  
Becky Skidmore ◽  
...  

ABSTRACT Introduction Musculoskeletal injuries (MSKi) are a common challenge for those in military careers. Compared to their male peers, reports indicate that female military members and recruits are at greater risk of suffering MSKi during training and deployment. The objectives of this study were to identify the types and causes of MSKi among female military personnel and to explore the various risk factors associated with MSKi. Materials and Methods A scoping review was conducted over a 4-month time frame of English language, peer-reviewed studies published from 1946 to 2019. Search strategies for major biomedical databases (e.g., MEDLINE; Embase Classic + Embase; and the following EBM Reviews—Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, Database of Abstracts of Reviews of Effects, Health Technology Assessment, and the NHS Economic Evaluation Database) were developed by a senior medical information specialist and included 2,891 titles/abstracts. Study selection and data collection were designed according to the Population, Concept, and Context framework. Studies were included if the study population provided stratified data for females in a military context. Results From a total of 2,287 citations captured from the literature searches, 168 peer-reviewed publications (144 unique studies) were eligible for inclusion. Studies were identified from across 10 countries and published between 1977 and 2019. Study designs were primarily prospective and retrospective cohorts. Most studies assessed both prevalence/incidence and risk factors for MSKi (62.50%), with few studies assessing cause (13.69%). For MSKi of female recruits compared to active female members, the prevalence was higher (19.7%-58.3% vs. 5.5%-56.6%), but the incidence (0.02%-57.7% vs. 13.5%-71.9%) was lower. The incidence of stress fractures was found to be much higher in female recruits than in active members (1.6%-23.9% vs. 2.7%). For anthropometric risk factors, increased body fat was a predictor of MSKi, but not stress fractures. For physiological risk factors for both female military groups, being less physically fit, later menarche, and having no/irregular menses were predictors of MSKi and stress fractures. For biomechanical risk factors, among female recruits, longer tibial length and femoral neck diameter increased the risk of stress fractures, and low foot arch increased risk of an ankle sprain. For female active military members, differences in shoulder rotation and bone strength were associated with risk of MSKi. For biological sex, being female compared to male was associated with an increased risk of MSKi, stress fractures, and general injuries. The consequences of experiencing MSKi for active military included limited duties, time off, and discharge. For recruits, these included missed training days, limited duty days, and release. Conclusions This scoping review provides insight into the current state of the evidence regarding the types and causes of MSKi, as well as the factors that influence MSKi among females in the military. Future research endeavors should focus on randomized controlled trials examining training paradigms to see if women are more susceptible. The data presented in the scoping review could potentially be used to develop training strategies to mitigate some of the identified barriers that negatively impact women from pursuing careers in the military.


2018 ◽  
Vol 75 (5) ◽  
pp. 337-343 ◽  
Author(s):  
Julie Elbæk Pedersen ◽  
Kajsa Ugelvig Petersen ◽  
Niels Erik Ebbehøj ◽  
Jens Peter Bonde ◽  
Johnni Hansen

ObjectivesFirefighters are exposed to multiple cardiovascular hazards, but few epidemiological studies have addressed their cardiovascular morbidity. The objective of this study was therefore to examine the incidence of cardiovascular diseases (CVD) in Danish firefighters.MethodsWe used individual historical employment records on 11.691 male Danish firefighters supplied by trade unions and fire agencies. The Supplementary Pension Fund Register was used to establish two occupational reference groups (a random sample from the male employed population and military employees). Information on CVD incidence was retrieved from the nationwide Danish National Patient Registry. SIRs and Poisson regression analyses (incidence rate ratio) were used for estimation of risks, including 95% CIs.ResultsIn comparison with the population sample, the age-adjusted and calendar time-adjusted SIR for all CVDs combined was increased in firefighters (SIR=1.10, 95% CI 1.05 to 1.15). The risk was also elevated for the most frequent outcomes, including angina pectoris (SIR=1.16, 95% CI 1.08 to 1.24), acute myocardial infarction (SIR=1.16, 95% CI 1.06 to 1.26), chronic ischaemic heart disease (SIR=1.15, 95% CI 1.06 to 1.24) and atrial fibrillation/flutter (SIR=1.25, 95% CI 1.14 to 1.36). This analysis showed the most elevated SIRs for CVD in full-time firefighters compared with part-time/volunteer firefighters. Both types of firefighters employed <15 years had an increased risk of CVD. Similar risk patterns appeared in comparisons with the military. Internal analysis supported external findings.ConclusionThe risk of overall CVD, including the most frequent subtypes was modestly increased in Danish firefighters and was most elevated in full-time firefighters compared with other male employees.


Assessment ◽  
2018 ◽  
Vol 26 (6) ◽  
pp. 963-975 ◽  
Author(s):  
Ian H. Stanley ◽  
Jennifer M. Buchman-Schmitt ◽  
Carol Chu ◽  
Megan L. Rogers ◽  
Anna R. Gai ◽  
...  

Suicide rates within the U.S. military are elevated, necessitating greater efforts to identify those at increased risk. This study utilized a multigroup confirmatory factor analysis to examine measurement invariance of the Military Suicide Research Consortium Common Data Elements (CDEs) across current service members ( n = 2,015), younger veterans (<35 years; n = 377), and older veterans (≥35 years; n = 1,001). Strong factorial invariance was supported with adequate model fit observed for current service members, younger veterans, and older veterans. The structures of all models were generally comparable with few exceptions. The Military Suicide Research Consortium CDEs demonstrate at least adequate model fit for current military service members and veterans, regardless of age. Thus, the CDEs can be validly used across military and veteran populations. Given similar latent structures, research findings in one group may inform clinical and policy decision making for the other.


2021 ◽  
pp. bmjmilitary-2021-001945
Author(s):  
Iain Parsons ◽  
J Ellwood ◽  
M J Stacey ◽  
N Gall ◽  
M Grundy-Bowers ◽  
...  

IntroductionReflex syncope is the most common subtype of syncope and, despite not being associated with increased mortality, often results in significant morbidity and costly diagnostics. Reflex syncope can be of concern for certain occupational groups and may be exacerbated by some occupations. Reflex syncope in the military is anecdotally common but the extent in the UK Armed Forces (UKAF) is unknown. The aim of this study was to assess the incidence and prevalence of reflex syncope in the UKAF.MethodsA retrospective search of the Defence Medical Information Capability Programme using prespecified read-codes was performed at defence primary healthcare centres over the period of 1 January 2019 to 1 January 2020. Data were obtained on 76 103 service personnel (SP) (53% of the UKAF).ResultsThe overall syncope case rate for the UKAF was 10.5 per 1000 person-years (p-yrs). In comparing services there was a significantly increased risk of syncope in the British Army (10.7 per 1000 p-yrs) compared with the Royal Air Force (8.6 per 1000 p-yrs) (p=0.0365), SP who served overseas (16.7 per 1000 p-yrs) in comparison with UK medical centres (10.3 per 1000 p-yrs) (p<0.0001), and British Army units that regularly took part in State Ceremonial and Public Duties (15.8 per 1000 p-yrs vs 10.2 per 1000 p-yrs) (p=0.0035). Army training units conferred a significantly reduced risk of syncope (p<0.0001).ConclusionsThese data are the first to define the incidence and prevalence of syncope in the UKAF. Orthostasis and heat are probable triggers, although recruits are potentially protected. These data offer opportunities to improve the health and well-being of SP, with economic, logistical and reputational benefits for the UKAF. Further research to identify personnel at risk of future syncopal events may allow for targeted use of countermeasures.


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