|Year : 2017 | Volume
| Issue : 1 | Page : 9-14
Mobile phones for mobility or morbidity: Is there an evidence for morbidity?
Naresh K Panda1, Karan Gupta1, Sourabha K Patro1, Roshan Verma1, Sanjay Munjal1, Jaimanti Bakshi1, P. V. M. Laxmi2
1 Department of Otolaryngology, Postgraduate Institute of Medical Education and Research, Chandigarh, India
2 Department of Community Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh, India
|Date of Web Publication||8-Nov-2017|
Naresh K Panda
Department of Otolaryngology and Head and Neck Surgery, Postgraduate Institute of Medical Education and Research, Chandigarh
Source of Support: None, Conflict of Interest: None
Objectives: Potential health risks are posed by long-term electromagnetic exposure due to mobiles. This study was undertaken to assess changes in the hearing at the level of the inner ear and central auditory pathway due to chronic exposure to the electromagnetic waves from mobile phones using both global system for mobile communication (GSM) and code division multiple access (CDMA) types of mobile technology. Study Design: Cross-sectional study. Materials and Methods: A total of 321 individuals who were long-term mobile users (more than 1 year, 238 GSM and 83 CDMA) and 46 individuals who had never used mobile phones underwent investigations including pure tone audiometry (500 Hz to 16 KHz), distortion product otoacoustic emissions (DPOAEs), auditory brain responses, and middle latency responses (MLR). The changes in the parameters were studied in mobile and nonmobile using ears of both GSM and CDMA individuals and corresponding ears of the controls to ascertain the effects of electromagnetic exposure. Results: GSM and CDMA users had a higher risk of having DPOAE absent as compared to controls (P = 0.000) more so if used longer during the day. They were found to have higher speech frequency thresholds and lower MLR wave Na amplitudes. More than 3 years of use emerged as a risk factor (P < 0.05). The damage was bilateral. Individuals using CDMA phones had more high-frequency loss than GSM user. The amplitudes of waves in MLR were lower in mobile phone users than nonusers. Conclusions: Long-term GSM and CDMA mobile phone use is associated with damage to the cochlea and auditory cortex.
Keywords: Auditory effects, electromagnetic radiations, mobile phones
|How to cite this article:|
Panda NK, Gupta K, Patro SK, Verma R, Munjal S, Bakshi J, Laxmi P. Mobile phones for mobility or morbidity: Is there an evidence for morbidity?. Ann Indian Acad Otorhinolaryngol Head Neck Surg 2017;1:9-14
|How to cite this URL:|
Panda NK, Gupta K, Patro SK, Verma R, Munjal S, Bakshi J, Laxmi P. Mobile phones for mobility or morbidity: Is there an evidence for morbidity?. Ann Indian Acad Otorhinolaryngol Head Neck Surg [serial online] 2017 [cited 2019 Mar 23];1:9-14. Available from: http://www.aiaohns.in/text.asp?2017/1/1/9/217840
| Introduction|| |
Mobile telephones have been available since 1983, and their usage has spread widely and rapidly. It is expected that the number of users may reach to 6 billion by the end of 2015. Genuine concerns are being increased regarding potential health risks associated with the radiofrequency exposure while using these devices. The possible adverse effects of radiation exposure on the hearing system associated with mobile phone usage should be investigated, as the phones are usually held close to the ear. The external ear may provide a natural route by which emitted radiofrequency radiations may reach the peripheral and the central nervous system. Temperature variations in an external auditory canal in relation to body temperature (cooling and heating) can lead to depression of micromechanical activity of the outer hair cells in the cochlea., Most of the studies on electromagnetic radiations (EMRs) deal with effects secondary to short-term exposure (10 min to 1 h).,,,, There is a dearth of medical literature on the effects of chronic mobile phone usage on hearing loss. Only a few studies have been performed to date.,,, Based on the results of their studies, Davidson and Lutman  and Sievert et al. did not report any audiological abnormalities in chronic mobile phone users. Our center has published the results of a study of audiological disturbances in long-term mobile phone users. High-frequency hearing loss and absent distortion product otoacoustic emission (OAE) were observed with an increase in the duration of mobile phone use more so in individuals of age >30 years. Another study by our department compared hearing loss with the duration of mobile use and the network the individuals were using, the presence of high-frequency hearing loss and absence of distortion product OAE (DPOAE) were seen with both global system for mobile communication (GSM) and code division multiple access (CDMA) networks. This study was conducted to assess potential changes in hearing function due to chronic exposure to radiations associated with GSM and CDMA mobile phones in a larger group of individuals so as to characterize the nature of changes observed with long-term mobile phone use.
Physics of mobile telephony
The most commonly used technologies for mobile telecommunication are GSM and CDMA. Time division multiple access (TDMA; in GSM 2G) is accomplished by chopping up the channel into sequential time slices. Each user of the channel takes a turn to transmit and receive signals. In reality, only 1 person is actually using the channel at a specific moment.
CDMA uses a type of digital modulation called spread spectrum, which spread voice data over a wide channel in a pseudorandom fashion. The receiver undoes the randomization to collect the bits together and produce the sound. It is due to this fundamental difference that the two technologies cause different electromagnetic exposure to the user.
The GSM (TDMA) therefore enables a greater number of people to simultaneously communicate with a base station. This leads to an additional low-frequency pulsing of the signal at 8.34 HZ. Hence, a GSM user is exposed to electromagnetic waves in a continuous as well as pulsed manner.
CDMA uses code division for multiple accesses. There is continuous exposure to microwaves. However, the additional low-frequency pulsing of the signal is absent.
| Materials And Methods|| |
This cross-sectional study was conducted between January 2011 and March 2014 in the Department of Otolaryngology and Head and Neck Surgery, Postgraduate Institute of Medical Education and Research, Chandigarh, India. It included 381 individuals who had been using mobile phones regularly at least for more than a year. Their age ranged from 18 to 70 years. Due to malfunctioning of the OAE apparatus, OAES could not be done in sixty participants. Hence, these sixty patients were excluded from the study and analysis was performed for only 321 individuals. Two hundred thirty-eight participants used GSM phones and 83 used CDMA phones. Forty-six individuals who had never used mobile phones acted as controls. It was also ensured that the controls had never used Bluetooth headsets or mobile phones in speaker mode as even used with a headset or speaker there is radiation exposure for the individuals. Informed consent was obtained from all the subjects. The study was cleared by the Institute Ethics Committee.
The individuals were recruited from hospital visitors and people who responded to an awareness campaign about the health effects of mobile phones. There was no specific randomization method used for selection of individuals as all those individuals had responded to an awareness campaign. Persons with a history of ear discharge, any kind of ear pathologies, previous ear surgery, with history of ototoxic medications, prolonged noise exposure, i.e., those working in the noisy places including those in armed forces, having history of head trauma or any other neurologic or neurosurgical disease and those having any systemic disease that might affect hearing were excluded. Individuals who were not excluded were taken for the study. We ensured that the individuals who reported to us and consented for the study were not outpatient department visitors of other specialty clinics to avoid any bias. All the individuals were evaluated after a thorough history and clinical examination.
Mobile phone users were asked about the preferential ear of use, total cumulative usage in a number of years, average daily use in minutes and the monthly average bill.
After excluding external and middle ear pathology, the patients underwent audiological investigations, which included pure tone audiometry (PTA) (250 Hz 50 16 kHz), speech discrimination scores, speech reception thresholds, impedance audiometry, DPOAE, auditory brain response (ABR), and middle latency responses (MLRs). The persons performing these audiological investigations were blinded about the groups the patients belonged to.
The individuals in each group (i.e., GSM and CDMA) were divided on the basis of total duration of mobile phone use G1 (<3 years) and G2 (>3 years) in GSM users and C1 (<3 years) and C2 (>3 years) in CDMA users. In each category, the individuals were further subdivided on the basis of daily mobile phone usage into heavy (Group 3) (>60 min), moderate (Group 2) (30–60 min), and light (Group 1) (<30 min) users. The changes in PTA, speech audiometry, OAEs, ABR and MLR, were studied in the mobile phone using ear and nonmobile phone using ears and the corresponding ears of the control individuals.
Descriptive statistics was used to summarize the data. The quantitative variables were described using means and their 95% confidence intervals. Outcome variables of DPOAE and presence or absence of acoustic reflexes were tested for association with categorical variables (mobile users vs. control, heavy vs. light users) using Chi-square, Fisher's exact, and McNemar tests. Univariate odds ratios were calculated for these variables. Further quantitative variables among two groups of cases and controls were simultaneously compared using one-way analysis of variances with post hoc analysis (Tuckey and Dunnett) where ever significant relationships were found. Quantitative variables of PTA thresholds, ABR and MLR latencies were analyzed for subgroups according to the duration of mobile use using one-way analysis. All results were two-tailed, and P < 0.05 was considered statistically significant. SPSS version 20.0 (IBM Corporation, Armonk, NY, 2011) was used for analysis of the data.
| Results|| |
The mean age of mobile users and controls were 31.19 ± 8.68 and 30.07 ± 8.99 years, respectively. The male to female ratio in cases did not differ significantly from that of controls. The distribution of participants in various groups on the basis of their daily mobile usage is as follows.
Forty-seven subjects used their mobiles <30 min/day, 52 subjects used between 30 and 60 min/day and 222 individuals used for more than 60 min per day, making a total of 321 individuals in the study group.
On PTA, no significant differences were seen between the controls and both GSM and CDMA users in lower frequencies, but at higher frequencies from 12000 to 16000 Hz the mean pure tone thresholds were significantly higher for GSM users were 50.18 ± 22.32 dB (t = 4.351, P = 0.000) and for the CDMA users was 55.95 ± 20.09 dB (t = 6.709, P = 0.000) than the average of the controls [35.81 ± 2.73 dB, [Table 1]. The mean pure tone threshold of 55.95 dB in CDMA mobile users in higher frequencies were significantly higher than the mean threshold 50.18 dB of GSM mobile users [P = 0.037, t = −2.090, [Table 1].
|Table 1: Mean pure tone thresholds at high frequency among controls, global system for mobile communication and code division multiple access users in the mobile using ear|
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On studying the total duration of mobile phone usage on hearing, it was seen that individuals using mobile phone for more than 3 years had significant higher losses on PTA than those who had used for <3 years [P < 0.05, [Table 2].
|Table 2: Comparison of pure tone thresholds between Groups I (<3 years) and II (>3 years) based on total duration of use of mobile phones|
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On comparison of DPOAE results between mobile phone users of both GSM and CDMA types of mobile phones and controls in both right and left ear showed significantly high rates of absence of DPOAE among mobile phone users compared to that of the controls [Table 3]. Interestingly, there was no difference between GSM and CDMA networks in terms of the absence of DPOAE. 32/83 (38.55%) using CDMA network had absent DPOAE compared to 89/238 (37.39%) using GSM network. The P value was 0.476 using Fisher's exact test. On comparing the DPOAE with duration of mobile use per day, it was seen that in the mobile phone using ear (right), there was a significant chance of DPOAE being associated with the hours of use, especially in those using for more than 60 min duration. However, the similar difference was not seen in the nonmobile phone using ear [Table 4].
|Table 3: Comparison of distortion product otoacoustic emissions between mobile phone user (global system for mobile communication and code division multiple access) and controls|
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|Table 4: Distortion product otoacoustic emissions compared to the duration of mobile phone use per day in participants|
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Comparing the DPOAE in the mobile using ear in GSM individuals (right ear) with respect to duration of daily usage, it was seen that GSM individuals with an average daily use of more than 1 h were 3.15 times more likely to have DPOAE absent in the mobile phone using ear than individuals with an average daily usage of <1 h. This finding was statistically significant (P < 0.05) similar results were seen regarding average daily use in CDMA users.
On studying the MLRs in mobile using ears (right ear) and corresponding ears in the control population, GSM and CDMA individuals were found to have significantly lower mean MLR Na wave latencies and mean Pa wave latencies. This significant lower value was consistent for both CDMA and GSM users both alone and together compared to that of the controls [P < 0.05, [Table 5].
|Table 5: Comparison of middle latency responses wave Na latencies between mobile using ear in mobile phone users (global system for mobile communication and code division multiple access) and controls|
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Analysis of various risk factors was also carried out for their significance. The MLR parameters were compared between study populations by taking into account the total cumulative usage in years. CDMA phone users with usage >3 years differed significantly (P < 0.05) from those who have used for <3 years in having lower wave Na latencies in MLR [Table 6].
|Table 6: Comparison of middle latency responses wave Na latencies with respect to cumulative use in duration in code division multiple access and global system for mobile communication users|
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The latencies of waves I, III and wave V and interpeak latencies were found to be prolonged in the mobile phone user as compared to the controls, but the differences did not reach statistical significance. The latencies were also evaluated according to the mobile network and duration of use per day. There was no difference between the two networks, i.e., GSM and CDMA in the three groups based on the duration of mobile phone use per day [Table 7] and [Table 8].
|Table 7: Comparison of auditory brain responses wave latencies between global system for mobile communication and code division multiple access users based on their duration of use per day|
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|Table 8: Comparison of auditory brain responses wave latencies between global system for mobile communication and code division multiple access users in each ear|
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However, statistically significant prolonged wave V latency was noticed in individuals with daily usage more than 60-min compared to those using <60 min. This was seen in both mobile and nonmobile using ears in GSM users. However, there was no difference in CDMA users [Table 7].
Rest of the audiological parameters including amplitude and interwave latencies of ABR, acoustic reflex, tympanometry were found comparable between the controls and individuals using mobile phones.
| Discussion|| |
There is growing concern that the prolonged use of mobile phones can be detrimental to hearing. The inner ear is probably the first and main organ that receives the full impact of EMR due to its proximity. The delicate hair cells may be more vulnerable to injury compared to other structures. This study has been carried out with the aim of finding whether the use of mobile phones has an effect on the hearing mechanism, especially after prolonged usage.
OAEs are low-intensity acoustic signals emitted by the healthy cochlea. OAE is a reliable method to assess in vivo cochlear functionality. This study has revealed that the GSM and CDMA individuals are at higher risk of having absent DPOAE compared with the control population (P < 0.05). On the contrary, Aran et al. and Kizilay et al. did not report any changes in OAES secondary to radio frequency exposure. However, similar results were reported in an earlier study from our department which also showed the significantly higher risk of absent DPOAE in the mobile using individuals compared to controls. The variability in this finding could be due to the difference in the total cumulative duration of usage. This study included users with at least 1 year of usage. DPOAE were considered absent when 3 consecutive frequencies failed to show signal to noise ratio >3 dB. However, larger numerical data with frequency specific SNRs would be more contributory. This can be undertaken in future studies.
The prolongation of wave V latency seen in prolonged usage per day in GSM users in both mobile ear and nonmobile ear could herald subtle changes in the auditory pathway. However, change in wave V alone is difficult to explain but may be viewed with seriousness if associated with other auditory abnormality.
A significant loss in higher speech frequencies and absence of DPOAE in mobile phone users with essentially normal ABR could indicate the site of primary insult to be at the outer hair cells. This was seen as in our study where other than an abnormality in wave V other wave latencies were grossly normal in the study.
Two factors had a significant impact on the magnitude of auditory dysfunction secondary to mobile phone usage. In the first place, total cumulative use equal to or more than 3 years was found to be a risk factor associated with absent DPOAE, higher pure tone audiometric thresholds and lower wave Na amplitude in MLR (P < 0.05). Second, average daily usage more than 1 h was also found to be a risk factor for the absence of DPOAE in the mobile using ear as compared with users with an average daily use of 30–60 min.
The MLR is used to assess the subcortical and cortical areas above the level of the brain stem. These originate from thalamocortical projection and the temporal auditory cortex. The analysis of the Na component of MLR has the advantage of evaluating the integrity of the primary auditory cortex within the temporal lobe. Any amplitude changes in the Pa component of the MLR may reflect disturbances within both the subcortical and cortical regions of the auditory cortex. These regions are also likely to be much exposed to the pulsed electromagnetic field from a mobile phone because they are near the antenna of the phone. Our results have shown lower Na wave amplitude in both GSM and CDMA users (P < 0.05). However, Arai et al. did not find any significant differences in MLR secondary to short-term mobile phone use.
The changes in various audiological parameters were found to be comparable between the mobile phone using ear and nonmobile using ear for both the GSM and CDMA users. This is similar to what has been reported in the context of GSM users. Both GSM and CDMA phones operate in the range of about 800–900 MHz Thus, the distance in which the microwaves have their maximum energy comes out to about 33–37 cm (1 wavelength), which covers the whole head. This could be a probable reason for the bilateral effect.
The subjects in the study group belonged to the same geographic region. It can be presumed that they had a comparable noise exposure. It is thus possible that with little or no difference in the prevalence of this factor, the changes in the audiological parameters could be due to the cell phone use.
The strength of this study lies in the fact that none of the other studies have evaluated effects of CDMA mobile phone usage on hearing or compared the changes with GSM phone usage. The present study with large sample size validates the results of a similar study reported earlier. Moreover, pronounces the ill effects of long-term mobile phone use on hearing and auditory pathway. We do have a comparable control population, which is becoming difficult to obtain due to an increasing high teledensity. A relatively higher rural population in the vicinity helped us in this regard.
| Conclusions|| |
This study raises some questions regarding the issue of effects of mobile phones on hearing. The mobile phone users were found to have a subclinical hearing loss, which could be bilateral. Certain risk factors emerged that could be detrimental to hearing. They were more related to the duration of usage (both daily and cumulative) than the type of communication protocol used (GSM or CDMA).
Indian Council of Medical Research, New Delhi for grants.
Financial support and sponsorship
Grant in aid from Indian Council of Medical Research, New Delhi, India.
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8]