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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 26  |  Issue : 1  |  Page : 20-26

Study of brainstem evoked response audiometry in medical students having long time mobile usage


1 Department of Physiology, Mahatma Gandhi Institute of Medical Sciences, Wardha, Maharashtra, India
2 Mahatma Gandhi Institute of Medical Sciences, Wardha, Maharashtra, India
3 Department of Physiology, Anatomy, Mahatma Gandhi Institute of Medical Sciences, Wardha, Maharashtra, India

Date of Submission21-Jan-2019
Date of Acceptance26-Mar-2019
Date of Web Publication19-Feb-2020

Correspondence Address:
Dr. Ruchi Kothari
Department of Physiology, Mahatma Gandhi Institute of Medical Sciences, Sevagram, Wardha - 442 102, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/indianjotol.INDIANJOTOL_6_19

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  Abstract 


Background: Mobile phones are undoubtedly one of the most revolutionizing inventions of the 21st century and are indispensable communication tools. Concomitantly, there has also been a potential increase in the health risks associated with prolonged mobile phone usage. Electromagnetic radiations emitted from telecommunication systems absorbed by the recipient's body may bring about changes in the brain electrical activity. Brainstem evoked response audiometry allows quantifying the activity of auditory pathway, and hence, the present study was undertaken to evaluate the auditory evoked potentials in the MBBS students who have been long-term mobile users.
Materials and Methods: The study was conducted using Evoked Potential Recorder (RMS EMGEP MARK-II) in the Neurophysiology unit, Department of Physiology, Mahatma Gandhi Institute of Medical Sciences. This was an observational noninterventional study design incorporating a total of 50 MBBS students, from institutional campus using mobile phones for >1 year. 25 students who used mobile phones for <30 min/day formed the controls whereas, 25 students who used mobile phones for >30 min/day formed the test group. Results: The mean age among the test group was 17.5 ± 1.4 years and among controls was 16.2 ± 2.0 years. The average latency (both the right and left ear) of waves I–V and interpeak latencies (IPLs) I–III, III–V, and I–V waves were found to be prolonged (P > 0.001) in the test group when compared to controls. The mean latencies of the left ear were significantly (P < 0.05) prolonged as compared to the right ear in the test group. Conclusion: This study revealed that there is a significant prolongation in the absolute latencies and IPLs in mobile phone users associated with the duration of usage.

Keywords: Brainstem evoked response audiometry, interpeak latency, medical students, mobile phone


How to cite this article:
Kothari R, Karwande A, Bokariya P. Study of brainstem evoked response audiometry in medical students having long time mobile usage. Indian J Otol 2020;26:20-6

How to cite this URL:
Kothari R, Karwande A, Bokariya P. Study of brainstem evoked response audiometry in medical students having long time mobile usage. Indian J Otol [serial online] 2020 [cited 2020 Mar 29];26:20-6. Available from: http://www.indianjotol.org/text.asp?2020/26/1/20/278737




  Introduction Top


Mobile phones are undoubtedly one of the most revolutionizing inventions of the 21st century and are indispensable communication tools. They are more than just a status symbol and have become a necessity in today's world. The mobile a decade ago was simply used for the purpose of making a phone call or sending short messaging service and was known as a feature phone, but now a mobile is virtually a minicomputer, even better than some actual computers and it supports many additional features such as camera, MP3 Player, radio, Internet access, gaming, and Global Positioning System (GPS) to name a few. With these enormous technological developments in mobiles, there has also been a potential increase in the health risks associated with prolonged mobile phone usage. As of 2016, there are 1.02 billion mobile users in India.[1] Mobiles communicate by transmitting and receiving electromagnetic (EM), radio waves at frequencies of about 900 MHz to 1800 MHz. Many recent studies have raised questions regarding the safety of such radio frequency–EM waves (RF–EMWs) exposure to humans.[2] Increased use of mobile phones has also raised concerns about alteration of cognitive functions and neural activity. It has been documented that EM radiations (EMRs) emitted from telecommunication systems absorbed by recipient's body cause and bring about changes in the brain electrical activity, sensations of burning or warmth around the ear, and alteration of the blood–brain barrier.[3] EM field (EMF) radiations may cause adverse health problems such as headache, sleep disorders, impairment of memory, lack of concentration, dizziness, increased frequency of seizures in epileptic subjects, and high blood pressure.[4] Any EMR relevant to mobile phone usage is described in terms of specific absorption rate (SAR) with units of W/kg which is the amount of energy absorbed by a unit mass of the object.[5] SAR is a measure of the rate of RF energy absorption by the body from the cell phone. It provides a means for measuring the RF exposure characteristics of cell phones to ensure that they are within the safety guidelines. Although the effects of acute exposure of mobile phones on hearing have been studied, scanty data exist regarding chronic exposure of EMFs generated by mobile phones. Cochlear nerves and temporal lobes are the neural structures most exposed to the EMF emitted by mobiles. Being nearest to the mobile phone, ear is the most vulnerable organ of the body for high SAR deposition.[6] The use of mobile phone by bringing it closer to the ear increases the SAR of the waves and thus, the amount of output energy absorbed by the head may rise as high as 40%–55%,[7] so the mobile phones are ideally positioned to affect the auditory system.

Brainstem evoked response audiometry (BERA) allows quantifying the activity and functions of auditory pathway emerging from the auditory nerve up to the subcortical centers. These are potentials recorded from ear and vertex in response to brief auditory stimulation to assess conduction through the auditory pathway to the level of the midbrain. It is a simple noninvasive procedure to detect early impairment of the acoustic nerve and auditory pathway.

A couple of studies have been conducted across the country, wherein the effect of prolonged use of mobile phones on BERA has been assessed, but they are contradictory to each other with respect to their conclusions. Gupta et al., in Punjab, conducted a retrospective cross-sectional, case-control study on 100 students and concluded that long-term usage of mobile does not affect BERA.[8] Sevi et al., in Chennai, performed a study on 173 students and reported that prolonged use of mobile phones leads to abnormalities in the conduction of electrical signals in different levels of the auditory pathway.[9] Ramya et al., in Karnataka, studied 50 students who were long-term mobile users and found a significant increase in their hearing threshold.[10]

Aim

Due to such conflicting studies, there is a dearth of information on the influence of chronic mobile phone usage on the integrity of the auditory pathway. Hence, the present study was undertaken with an aim to evaluate the brainstem auditory evoked potentials in the budding doctors that is MBBS students of MGIMS who have been long-term mobile users to advance our understanding of the potential effects of mobile phones on them.

Objectives

The objectives of the study were as follows:

  1. To study BERA parameters in a cohort of medical students of MGIMS
  2. To assess and compare the amplitude of BERA waves in the study groups
  3. To assess and compare interpeak latencies (IPLs) of BERA waves in the study groups.


Exposure to RF signals generated by the use of cellular telephones have increased dramatically and reported to affect physiological, neurological, and cognitive and behavioral changes and to induce, initiate, and promote carcinogenesis. Although there is still no consensus about the causal relationship of RF–EMWs and brain tumors. It has been reported that there is increased risk of acoustic neuroma associated with mobile phone use of at least 10 years duration.[11]

Some clinical trials also suggest a possible link to increased risk of vehicular accidents, leukemias, and sleep disturbances.[12] A couple of recent studies using positron-emission tomography have demonstrated a decrease in regional cerebral blood flow on the side of the use of mobile phone.[13] Long-term mobile phone use cause damage to cochlea as well as the auditory cortex.[14] It has also been documented to produce DNA fragmentation in human fibroblasts and sperms, suggestive of genotoxic effect.[15]

However, Sievert et al., in 2007,[16] did not to observe abnormalities in the inner ear from cochlea to inferior colliculus in their study population (mobile phone users). According to Uloziene et al.[17] and Bak et al.,[18] acute exposure of EMR emitted from a mobile phone does not produce immediate effect and measurable hearing deterioration in young students. Similarly, a study was done on the student population in the UK by Davidson and Lutman[19] on the adverse effects of mobile phones on the auditory pathway. Daily usage ranged between 0 and 45 min. The results of the present study stated that there were no harmful effects of mobile phone usage on their audiovestibular systems within the range of exposure of the study.

In contrast, a study carried out in the USA, UK, New Zealand, and Australia showed that the major complaints of mobile phone users include headache, fatigue, general ill-being, muscular pains, and nausea. The EMF of the microwave frequency, as well as the frequency emitted by mobile phones, may be responsible for various biological effects.[20]

Hence, the use of mobile phones and the consequent biological effects and/or risks, cannot be restricted to the domains of personal lifestyle but involves the whole population and should be considered as a high priority environmentally related health issue.[21]

The meager amount of research regarding the evaluation of the auditory system among the student community shows that there is a big interval in the knowledge of potential effects of longtime mobile phone use on hearing. Hence, the present study aims to assess the brainstem evoked potential changes as a consequence of long time usage of the mobile phone.


  Materials and Methods Top


Study design

This was an observational noninterventional study design for the purpose of data collection incorporating a total of 50 MBBS students. The study was conducted in the Neurophysiology unit of the Department of Physiology, MGIMS. Mahatma Gandhi Institute of Medical Sciences is a rural Medical College and hospital located in a village, Sevagram in Wardha District in central India.

Study population

The study population consisted of 50 students recruited for the study which were divided into two categories (each with 25 students) according to the duration of mobile usage:

  • Test group: Who used mobile for >30 min/day for the duration of 1 year
  • Control group: Who used mobile for <30 min/day for the duration of 1 year.


Inclusion criteria

  1. Apparently healthy controls with normal hearing
  2. No past/present history of any ear disease or deafness
  3. Chronic mobile phone users using Global System for Mobile (GSM) mobile phones for >1 year.


Exclusion criteria

  1. Students having a history of otological diseases such as discharge and hearing loss ear surgery
  2. Exposure to prolonged loud noise
  3. Intake of the ototoxic drug, head injury
  4. Family/own history of the familial hearing disorder, deafness
  5. Any systemic disease known to cause hearing loss
  6. Any disease known to affect the study like diabetes mellitus, hypertension, and brain injury
  7. Those not willing to study participation were excluded from the study.


Diseases were excluded by taking their history, general physical examination, and audiological examination by consultant otolaryngologist.

Measurement methodology

We collected data with structured questionnaire to all participants. We took a complete clinical history and did physical examination in all the study participants. In all participants, BERA study was performed by RMS EMG (EP MARK-II) available in clinical Neurophysiology unit, Department of Physiology, Mahatma Gandhi Institute of Medical Sciences, Sevagram.

Procedure for brainstem evoked response audiometry recording

  • The standard procedure which is performed to carry out BERA was followed
  • Subjects were placed in a supine position on the examination bed
  • Patient's hair had to be oil free because electrodes had to be placed over the head
  • Surface electrodes filled with conducting jelly or paste is preferred
  • Non-inverting (reference) electrode was placed on the vertex of the head and inverting (active) electrodes were placed over the ear lobe or mastoid prominence one more ground electrode were placed over the forehead
  • Stimulus either in the form of click or tone pip is transmitted to the ear through a transducer placed in the insert earphone
  • BERA was recorded using amplification of 200,000–500,000
  • Electrical activity was filtered with a low filter frequency at 100 Hz and high filter frequency at 3 KHz
  • Recordings were done through monoaural stimulation by giving 90 dB stimulation to examining ear. The contralateral ear was always masked with white noise 40 dB below the ipsilateral click stimuli to get a correct response
  • Analysis time was 10 ms with a sweep speed of 1 ms/division
  • At least two recordings were taken for each ear
  • The waveforms of impulses generated at the level of brainstem were recorded
  • 2000 stimulations were applied to both ears, and the average of them was accepted as BERA response.


Classical brainstem evoked response audiometry waveform

Classical BERA comprises five or more waves within 10 ms of the stimulus which are labeled by Roman numerals. Initial five waves are clinically important and succeeding peaks VI–VII are quite variable. A normal BERA waveform consists of Wave I from VIII nerve (acoustic nerve), Wave II from the cochlear nucleus, Wave III from superior olivary complex, and Wave IV from nucleus of lateral leminiscus. Wave V from inferior colliculus, Wave VI is from the medial geniculate body, and Wave VII originates between the medial geniculate body to auditory complex.

The following parameters were determined:

  1. Absolute latencies and amplitude: Absolute latencies are measured from the peak of the respective wave. Absolute amplitudes are measured from the peak to the trough
  2. IPL: IPL is a latency difference between waves. The most common IPLs used are I–V, I–III, and III–V.


Data collection method

All the data were abstracted on a standardized data collection form. We used MS Excel spreadsheet to enter the data electronically. Questionnaire was filled up by the subject to get the detailed history of mobile phone use like model of mobile phone for frequency variation, duration of mobile phone use (hours/day and years). Data of the BERA parameters were expressed as mean ± standard deviation.

Statistical analysis

The Chi-square test and Student's t-test for statistical significance was used to analyze the data using appropriate statistical software. Value of P< 0.05 was considered as statistically significant.

Ethics consideration

We obtained written informed consent from all the study participants. We ensured that consent is (a) given voluntarily, (b) fully informed, and (c) is obtained from the persons who are competent to do so. In the consent form, we will explain the aims of the study, the anticipated benefits and the risks, and the right to withdraw from the interview process at any time without any reprisals. The use of confidential patient data was fully within the recent guidelines from the Indian Council of Medical Research about the use of personnel information in medical research. We obtained ethics approval before conducting the study from the Institutional Ethics Committee of our institute.


  Results Top


The mean age among the test group was 17.5 ± 1.4 years and among controls was 16.2 ± 2.0 years. Males predominated over females among both the test and control groups with 80% in the test group and 72% in the control group. Majority of students were the right ear dominant with 88% in the test group and 76% in the control group. There was no significant difference was found between hearing thresholds on the dominant side compared with the nondominant side. There was a significant increase in the hearing thresholds at all frequencies in the right and left ear in the test group compared with the control group.

In the test group, although participants used mobile phone for less number of hours, their usage per day was found to be more [Table 1] when compared to that of the control group which was statistically significant. In the present study, the prevalence of mobile phone usage in the different age group of the study population, duration of mobile phone use in year and hours/day were also evaluated.
Table 1: Comparison of absolute latencies in brainstem evoked response audiometry control group in the left and right ear

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The results showed that the prevalence of mobile phone use was much lower in the control group (25%) when compared to test group (34%). The mobile phone usage prevalence was higher in test group (41%). The absolute latencies of BERA at Left and Right Ear in control group and test group have been compared in [Table 1] and [Table 2] respectively. These findings have been graphically illustrated in [Figure 1] and [Figure 2]. The average latency (both the right and left ear) of Waves I–V was found to be prolonged in test group when compared to that of controls. The reason for the differences could be due to differences in the ratio of hours/day of duration of mobile phone use between the two groups.
Table 2: Comparison of absolute latencies in brainstem evoked response audiometry test group in the right and left ear

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Figure 1: Comparison of absolute latencies in brainstem evoked response audiometry control group in the right and left ear

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Figure 2: Comparison of absolute latencies in brainstem evoked response audiometry test group in the right and left ear

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The comparison of absolute latencies in the two groups in right and left Ear has been depicted in [Table 3]. Its graphical depiction is given in [Figure 3].
Table 3: Comparison of absolute latencies in two groups in the right and left ear

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Figure 3: Comparison of absolute latencies in two groups in the right and left ear

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Prolonged latency of Wave I which originates from VIII nerve in test group showed peripheral hearing impairment in this study. In this study, the latency difference between I and V was shorter when compared to normal (4.5 ms) in all groups this could be due to conduction abnormality from proximal VIII nerve through pons to the midbrain. Prolonged I–III latency difference in the test group was susceptible to disorders affecting the proximal portion of VIII nerve pontomedullary junction, and lower pons around superior olive and trapezoid bodies.

EMRs exposure in the ear may delay the conduction from VIII verve across the subaracnoid space into the core of lower pons because mobile phones are directly held in the external ear.

The average range of frequency used by the subject in this study was 300–900 MHz which was considered as low frequency. It is apparent that low-frequency sound waves cause activation of basilar membrane near the apex of the cochlea. In fact, continuous exposure low-frequency sound waves from the mobile phones may destroy the entire apical half of the cochlea, which may destroy the basilar membrane where all the low-frequency sounds are normally detected.

The interpeak latencies of BERA at Left and Right Ear in control group and test group have been represented in [Table 4] and [Table 5] respectively. These findings have been graphically illustrated in [Figure 4] and [Figure 5].
Table 4: Comparison of interpeak latencies in brainstem evoked response audiometry control group in the right and left ear

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Table 5: Comparison of interpeak latencies in brainstem evoked response audiometry test group in the right and left ear

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Figure 4: Comparison of interpeak latencies in brainstem evoked response audiometry control group in the right and left ear

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Figure 5: Comparison of interpeak latencies in brainstem evoked response audiometry test group in the right and left ear

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The comparison of interpeak latencies in the two groups in right and left Ear has been depicted in [Table 6]. Its graphical depiction is given in [Figure 6].
Table 6: Comparison of interpeak latencies in two groups in the right and left ear

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Figure 6: Comparison of interpeak latencies in two groups in the right and left ear

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The absolute amplitudes of BERA at Left and Right Ear in control group and test group have been compared in [Table 7]. These findings have been graphically illustrated in [Figure 7].
Table 7: Comparison of absolute amplitudes in two groups in right and left ear

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Figure 7: Comparison of absolute amplitude in two groups in the right and left ear

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  Discussion Top


The present study was designed to investigate possible effects of long-term usage of mobile phones on the hearing of student users, as measured by changes in latencies, IPLs and amplitudes of BERA waves which represents the electrical activity of the distal portion of the auditory pathway from cochlear nerve to auditory brainstem and lateral lemniscuses of mid brain with five waveforms. We compared absolute latencies, IPLs, and amplitudes of BERA waves.

The average latencies (both the right and left ear) of Waves I–V were found to be prolonged in test group as compared to that of the control group. Prolonged latency of Wave I which originates from VIII nerve in the test group showed peripheral hearing impairment in this study. The delay in latencies from I to V could be due to conduction abnormality from proximal VIII nerve through pons to the midbrain.

Our findings corroborate with Sevi et al.[9] who also found a similar prolongation although the absolute latencies of the waves were on a higher side in the test group students when compared to theirs. These findings are also in agreement with a study by Panda et al.[22] who have also concluded that long-term mobile phone usage causes damage to cochlea and auditory cortex. Another study from Turkey by Oktay and Dasdag[23] also reported that a higher degree of hearing loss is associated with long-term exposure to EM field generated by cellular phones.

One conspicuous finding of the study is that the average latencies of the left ear were significantly (P < 0.05) prolonged as compared to right ear in the test group, which could be due to overuse of mobile phone on that side. Further, we also found that the absolute amplitudes were lower in the test group pointing to the fact that nerve conduction is impaired.

A couple of studies that contradict our findings are those of Khullar et al.,[24] Parazzini et al.[19] who have reported no detrimental effect of mobile usage on the auditory system.

Further, our study also showed prolonged IPLs I–III, III–V, and I–V. Prolonged I–III IPL is susceptible to disorders affecting the proximal portion of VIII nerve, pontomedullary junction, and lower pons around superior olive and trapezoid bodies. EMRs exposure in the ear probably delays the conduction from VIII verve across subarachnoid space into the core of lower pons, because mobile phones are directly held in the external ear. Another experimental study conducted by Kaprana et al.[25] in rabbits showed prolongation in the IPLs I–V and III–V as similar to our observations. It indicates that exposure to EMRs can affect the normal electrophysiological activity of the auditory system which is assessed by BERA and these findings fit the pattern of general responses to a stressor.


  Conclusion Top


From this study, it is concluded that students who used mobile phone for longer hours per day may suffer from conduction abnormalities in different levels of auditory pathway, lack of attention, cognition and intellectual activities. This study revealed that there is a significant prolongation in the absolute latencies and IPLs in mobile phone users associated with the duration of usage. Students who use mobiles for longer duration are more prone for earlier otological disturbances as they are exposed to the EMRs to the maximum.

Implication of the study

Avoiding mobile phones for longer hours per day can improve both physiological and psychological activities because the young generation in medical colleges are the budding doctors of future.

Future perspective

We propose the prudent use of mobile telephones by the young generation. Mobile telephones should be used only for short periods, and that too for essential purpose. The health impact of the mobile phone on each individual is variable as the population is genetically heterogeneous. Therefore, a further population-based study should be planned for future open end research.

Acknowledgment

We acknowledge and thank Maharashtra University of Health Sciences, Nashik for providing the Short Term Research Grant for the purpose of this research project.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]



 

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