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 Table of Contents  
ORIGINAL ARTICLE
Year : 2017  |  Volume : 6  |  Issue : 2  |  Page : 88-91

Do long-term noise exposure cause equilibrium problems? A cross-sectional study


Department of Surgery, College of Medicine, Taif University, Taif, Saudi Arabia

Date of Web Publication15-Sep-2017

Correspondence Address:
Sami A Al Kindy
Department of Surgery, College of Medicine, Taif University, P. O. Box 888, Taif 21974
Saudi Arabia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/sjhs.sjhs_28_17

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  Abstract 

Objective: The objective of the study was to assess the vestibular system among workers exposed to long-term noises.Design: This study design was a cross-sectional study. Setting: This study was conducted at Department of Otolaryngology, King Abdulaziz Special Hospital, Taif, Saudi Araia. Patients: The study involved two groups: long-term noise exposure group (N group), 126 workers, in a printing facility and a control group (Group C), 48 voluntaries, employee from a noise-free environment. Participants and Methods: Both groups had audiometrical and vestibular assessment using videonystagmograph (VNG) in a controlled environment. Results: Pure tone audiometry showed a significant reduction in N group high frequencies threshold compared with C group. Vertigo attacks were reported in 11 workers (24.4%) among the N group and VNG revealed six workers (13.3%) from N group diagnosed as peripheral insult while benign paroxysmal positional vertigo found in three workers (6.7%), while 36 workers (80%) in the same N group had normal “VNG” findings. Conclusion: Vestibular dysfunction may occur in workers with long-term chronic noise exposures.

Keywords: Hearing loss, noise, vertigo, videonystagmograph


How to cite this article:
Al Kindy SA. Do long-term noise exposure cause equilibrium problems? A cross-sectional study. Saudi J Health Sci 2017;6:88-91

How to cite this URL:
Al Kindy SA. Do long-term noise exposure cause equilibrium problems? A cross-sectional study. Saudi J Health Sci [serial online] 2017 [cited 2017 Dec 18];6:88-91. Available from: http://www.saudijhealthsci.org/text.asp?2017/6/2/88/214847


  Introduction Top


Noise, “is a sound, especially that is loud or unpleasant or causes disturbance” (Oxford Dictionary) and is considered to be the most biological stressors associated with everyday life with established harmful effect over 2500 years.[1],[2],[3]

A number of studies reported changes occurring in the inner ear as a result of noise-induced trauma including changes in its vascular supply and the biochemical state that can be either temporary or permanent.[4]

Noise-induced hearing loss (NIHL) in the majority of factory workers causes discomfort and may subsequently lead to psychological perturbations that can seriously affect the quality of life, not only the affected but also their relatives as well. This is probably an end result of cochlear lesion and damage to the vestibular end organs.[5],[6]

Vestibular-evoked myogenic potential (VEMP) demonstrated that saccule can be stimulated with sound levels at or above 100 decibel sound pressure level based on the fact that noise causing damage to the cochlea may also stimulate the balance system.[7],[8]

Moreover, both saccule and the Reissner's membrane had similar force stimulations, to noise, with the probability of balance system being affected more than that of cochlea.[9],[10]

The utricle, saccule, and semicircular canals in experimental animal model studies demonstrate that there was an obvious evidence of damage after the exposure to intense noise with destruction of the vestibular end organ.[11],[12]

Vestibular symptoms such as vertigo and dizziness may affect an individual's daily activities to a great extent (compared to hearing loss), and those with vestibular disturbances can be disabled with intolerance to their lifestyle system.[13]

Videonystagmograph (VNG) is an infrared video image computerized analysis technique used to record eye movements in three dimensions with advantages such as: noninvasive, requires little setup time, and is not associated with the position drifts requiring repeated calibrations.[14]

The objective of our study to evaluate prolonged noise exposure worker's vestibular system using VNG collected with sensory neural hearing loss pattern.


  Participants and Methods Top


The study was a cross-sectional study carried out in Otolaryngology Outpatient Department, King Abdulaziz Special Hospital, Taif, Saudi Arabia.

The study involved two groups; noise exposure group (N group), 126 employed in printing facilities with occupational noise exposure for more than 15 years (8 h a day and 6 days a week) and the control group (Group C), 48 voluntaries employee in a noise-free environment, who had 8 h a day, 6 days a week and none of them were exposed to hazardous noise at any point of their work.

Inclusion criteria were age above 12 years (for legal considerations), no clinically detected otolaryngology or medical abnormality that may cause balance disorders, no cervical or intracranial lesion, and not on sedatives (tranquilizers, vestibular suppressants, or balance disorders inducing drugs) within at least 48 hours before the VNG test or ototoxic drugs.

Both groups were given a questionnaire that included personal data, vertigo symptom, and severity of dizziness if present with respect to work environment, general health and habits.

Then, they were evaluated by hearing sensitivity test between 250 Hz and 8000 Hz as assessed on a pure tone audiometry tested using a calibrated Orbiter 922. “A” type tympanogram with normal acoustic reflex thresholds ensured normal middle ear function of all test groups.

Precipitants thereafter were subjected to otolaryngology history taking, complete clinical examination, basic audiometry “Orbiter 922 Version 2 Clinical Audiometer” “Madsen Electronics, Denmark” in a double-walled, sound-treated room using the “Hughson-Westlake” technique (Hughson and Westlake, 1981) (pure tone and speech) and finally VNG “International Commission on Stratigraphy medical VNG computerized analyzer, USA” (which include spontaneous nystagmus test, gaze-evoked nystagmus test, head positional test, saccade test sinusoidal tracking [ocular smooth pursuit] test, optokinetic test, Dix–Hallpike test (Dix and Hallpike, 1952), and bithermal caloric test.[15],[16]

Statistical analysis

Data collected were processed using SPSS version 15 (SPSS Inc., Chicago, IL, USA). Quantitative data expressed as means ± standard deviation (SD) while qualitative data expressed as numbers and percentages. Student's t- test is used to compare the significance of difference for quantitative variables that follow normal distribution.


  Results Top


The chronic noise exposed group (N group) 126 workers were employed in a printing facility (age ranged from 38 years to 59 years with a mean age of 44.9 years) with a history of occupational noise exposure of more than 15 years (8 h a day and 6 days a week) and the control 48 volunteers, (Group C) employees of noise-free environment (age range from 35 years to 55 years with a mean age of 41.3 years) who also had 8 h a day, 6 days a week none of them were exposed to hazardous noise at any point of their work.

The most frequent complaints among N group participants using visual analog scale (VAS) were tinnitus in 96 (76.2%), decrease in hearing acuity in 66 (52.4%), decrease in speech discrimination perception in 46 (36.5), and vertigo attacks in 39 (30.9%) who had vestibular symptoms, reported that vertigo came in attacks occurred five or seven times a week, and it lasted for 5 min with increased heart rate increased by the end of day work and relatively relieved during nonworking days.

There were no complaints among C group regarding the questionnaire evaluation using VAS. All participants in both groups had normal tympanometry and middle ear studies.

Pure tone audiometry showed a significant reduction in N group high frequencies threshold compared with C group [Table 1].
Table 1: Pure tone audiometry findings

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Spondee reception threshold and speech discrimination score show no significant difference between N group and C group.

Both groups were subjected to VNG study, Group C all had normal results, while in Group N, 12 (9.5%) were found to have peripheral insult, benign paroxysmal positional vertigo (BPPV) in 4 (3.2%), while 110 (87.3%) had normal “VNG” findings. No central or mixed lesion could be detected.

The C group (126)-associated vestibular dysfunction mean = 1.69 (SD = 0.464) compared to N group (46) mean = 2.00 (SD = 0.000) and to test the hypothesis that chronic noise exposure workers can have vestibular dysfunction, an independent t-test was performed, showed statically significant effect with P < 001.


  Discussion Top


Auditory dysfunctions constitute frequent complaints in the population studied, thereby reinforcing the need for permanently adopting both collective and individual preventive measures relating to exposure to noise. Furthermore, research and assessment of auditory dysfunction are fundamental in the occupational examinations of workers exposed to noise. Once NIHL has been established in the presence of an auditory dysfunction, such as tinnitus, it can be an important factor for causing suffering and negatively affecting the quality of life of workers.[15]

The balance function is controlled by cerebellum and the cortical structures apart from vestibular structures. In instances of vestibular end-organ damage, the compensatory strategies may be adopted by the central nervous system. Therefore, there is a real need to thoroughly examine the signs and symptoms presented by factory workers while taking history and clinical examination.[13]

As the exposure to noise increased, there was an increase in severity of dizziness. This is another supporting factor indicating that noise is the cause of dizziness in these workers. Another factor supporting the hypothesis is that in most instances, reduced hearing sensitivity and tinnitus are positively correlated. Coexistence of vestibular and otological symptoms strongly indicates that the vestibular and cochlear structures are gradually degenerating together due to chronic exposure to noise.[16]

An evidence to subclinical damage of the outer hair cells that may not be evident on a pure tone audiometry. This finding is in agreement with earlier studies.[17],[18],[19]

Vestibular symptoms exhibited by factory workers can be owed to the constant onslaught of noise on the ears of these workers; the symptoms exhibited by these workers are subtle due to which vestibular symptoms are neglected, and these symptoms do not affect their functional ability. Therefore, it is recommended that every person, who reports a history of exposure to occupational noise, is asked to complete a questionnaire such as the one used in the present study and investigated for vestibular symptoms.[13]

The interaction of physical therapy, occupational therapy, nursing, medicine, and audiologists to provide patients with the most complete care is ideal.[20]

The incidence of subjective cases reflects the occurrence of functional symptoms with no underlying pathophysiological changes and psychogenic factors in such cases should not be ignored as it may play an important role. This discrepancy between the subjective and objective vestibular findings indicates the presence of a psychological factor that may cause persistence of the balance disorder symptoms.[21]

Cases who developed BPPV are exposed to noise trauma and none of them are exposed to head trauma.

The unsteadiness and dizziness have a higher incidence in the subjective cases supporting the absence of a true vestibular lesion. It is clear that the vertigo was mainly in the moderate and severe cases while the unsteadiness and dizziness were only in the minor and mild cases.

All the cases with balance disorders are treated by medical treatment or by rehabilitation programs or by both according to the indications and contraindications explained before in the review of literatures.

Some of the cases developed BPPV have been treated medically, and the others have been treated by the modified Epley maneuver considered as a specific rehabilitation program for the BPPV cases.

Patients presenting with sound- or pressure-induced vestibular symptoms, a new entity has recently been suggested by Minor et al.[23] that exposure to noise may damage the vestibular receptors in the internal ear as well as those in the cochlea. The review covers lay and medical publications, observations on patients, experimental studies, and compensation claims. It concludes that the verdict must be “not proven” – that is, although such damage is possible, the evidence is not strong enough.[23]

Wu and Young (2009)[21] note the abnormal VEMP responses noted that above may have been related to saccular damage secondary to gunshot/noise exposure and they note the combined earplugs and earmuffs may not be sufficient to protect the saccule from long-term noise exposure.[24] Loud tones can damage the cochlea; however, vestibular involvement has been given less attention. Patients with NIHL may sometimes have balance disorders or symptoms resembling those of Meniere's disease episodic vertigo in NIHL patients, a pathophysiological mechanism similar to that of Meniere's disease.[25]


  Conclusion Top


Vestibular dysfunction may occur in workers with long-term chronic noise exposures.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

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Curthoys IS, Iwasaki S, Chihara Y, Ushio M, McGarvie LA, Burgess AM. The ocular vestibular-evoked myogenic potential to air-conducted sound; probable superior vestibular nerve origin. Clin Neurophysiol 2011;122:611-6.  Back to cited text no. 12
    
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Wu CC, Young YH. Ten-year longitudinal study of the effect of impulse noise exposure from gunshot on inner ear function. Int J Audiol 2009;48:655-60.  Back to cited text no. 21
    
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Zhang S, Liang Y, Liu X, Zhao J. Analysis with the logistic regression mode to the audiologic and vestibular functions in Meniere's disease. Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi 2011;25:452-6.  Back to cited text no. 22
    
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Minor LB, Solomon D, Zinreich JS, Zee DS. Sound-and/or pressure-induced vertigo due to bone dehiscence of the superior semicircular canal. Arch Otolaryngol Head Neck Surg 1998;124:249-58.  Back to cited text no. 23
    
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