|Year : 2011 | Volume
| Issue : 4 | Page : 159-161
Effect of mobile phone usage on hearing threshold: A pilot study
CS Ramya, Kutty Karthiyanee, Shankar Vinutha
Department of Physiology, Sri Devaraj Urs Medical College, Kolar, Karnataka, India
|Date of Web Publication||29-Mar-2012|
C S Ramya
No: 3038, CHS Building, New Extension, Kolar-563101, Karnataka
Source of Support: None, Conflict of Interest: None
Introduction: Mobile phones use electromagnetic radiation in the microwave range, which can be harmful to hearing. Earlier studies have showed an increase in hearing threshold with more than 30 minutes usage of mobile phones per day. Objective: To evaluate the relationship between the duration of usage of mobile phones per day and the change in auditory threshold. Materials and Methods: After obtaining institutional ethical committee clearance, 50 subjects, aged between 15 and 40 years, from institutional campus using mobile phones for more than 5 years were selected for this study. 25 subjects who used mobile phones for <30 min/day formed the control group, while 25 subjects who used their mobile phones for >30 min/day formed the test group. Pure-tone audiometry was done on all the subjects. Results: There was a significant increase in the hearing thresholds at all frequencies in air conduction and bone conduction in right ear in test group compared with the control group. Similarly, there was a significant increase in the hearing thresholds at all frequencies in air conduction and bone conduction in left ear also except for bone conduction at frequency 4 and 6 kHz. Conclusions: There is a significant increase in the hearing threshold in mobile phone users associated with duration of usage.
Keywords: Audiometer, Hearing, Mobile phones
|How to cite this article:|
Ramya C S, Karthiyanee K, Vinutha S. Effect of mobile phone usage on hearing threshold: A pilot study. Indian J Otol 2011;17:159-61
| Introduction|| |
Mobile phone as a communication tool has become an indispensable part of one's life these days. At the end of 2011, there were 6 billion mobile subscriptions, estimated by The International Telecommunication Union (2011) that is equivalent to 87% of the world population.  Of all anatomical structures, the ear has one of the closest proximity to mobile phones. Mobile phones use electromagnetic radiation in the microwave range, which affects hearing and also cause sensations of burning or warmth around the ear, headache, and disturbance of sleep. 
Therefore, the effect of mobile phone radiation on human health is the subject of recent interest and study, as a result of the enormous increase in mobile phone usage throughout the world.
So, this study was designed to evaluate the relationship between the duration of usage of mobile phones per day and the auditory threshold.
| Materials and Methods|| |
This study included 50 apparently healthy subjects in the age group 15-40 years using mobile phones for more than 5 years, taken from the Institutional Campus after obtaining ethical clearance from Institutional Ethical Committee and informed consent from them. Out of the 50 subjects taken, 25 subjects who used mobile phones >30 min/day were taken as the test group and 25 subjects who used mobile phones <30 min/day were taken as the control group.  Those with history of hypertension, diabetes, consumption of ototoxic drug, recent ear/nose/throat infection, noise-induced hearing loss (occupational), smoking, tobacco chewing, and symptoms related to hearing were excluded.
Pure-tone audiometry was done on these subjects in a silent room to evaluate the hearing threshold of each ear using an audiometer. Air conduction thresholds were measured for tones of 250, 500, 1000, 1500, 2000, 4000 6000, and 8000 Hz and bone conduction thresholds were measured for 250, 500, 1000, 1500, 2000, and 4000 Hz. The amount of intensity that has to be raised above the normal level is a measure of the degree of hearing impairment at that frequency. It is charted in the form of a graph called the "audiogram." The thresholds of bone conduction are a measure of the cochlear function. The difference in the thresholds of air and bone conduction (A-B gap) is a measure of a degree of conductive deafness. The audiometer is so calibrated that hearing of a normal person, both of air and bone conduction, is at 0 db and there is no A-B gap.
Subjects were made to wear earphones during air conduction testing and a vibrator during bone conduction testing. They were instructed to respond whenever and as soon as the tone comes on, regardless of how faint the tone is and to stop responding as soon as the tone goes off. They were told that one ear is tested at a time. A pulse of tone was presented at a set frequency and set dB hearing level using adjustment knobs on the audiometer. Mode of response was by a pressing button. The subjects were familiarized with the tone. After the first response, the tone was decreased by 10 dB whenever the subject responded and was increased by 5 dB if the person fails to respond. The bone vibrator for bone conduction checking was placed on the mastoid process, no closer than a thumb's width to prevent acoustic radiation and diagnostic testing at 250, 500, 1000, 2000, and 4000 Hz was done as above.
Interpretation of an audiogram was done as given below:
- Conductive deafness is indicated by raised air conduction thresholds (25 dB) and a normal bone conduction threshold with a wide air bone gap of 15 dB or more.
- Sensorineural deafness is indicated by raised air and bone conduction thresholds (both >25 dB) and the air bone gap does not exceed 10 dB.
- Mixed deafness air and bone conduction thresholds are raised with air bone gap of >15 dB. The data obtained were analyzed using paired t test.
Statistical calculations were done using statistical package for the social sciences (SPSS) version 14.
| Results|| |
The mean age among the test group was 18.2 ± 1.5 years and among controls was 17.2 ± 2.1 years. Males predominated over females among both the test and control groups with 80% in test group and 72% in control group. Majority of subjects were right ear dominant with 88% in test group and 76% in control group.
There was a significant increase in the hearing thresholds at all frequencies in air conduction and bone conduction in right ear in test group compared with control group. Similarly, there was a significant increase in the hearing thresholds at all frequencies in air conduction and bone conduction in left ear also except for bone conduction at frequency 4 and 6 kHz as shown in [Table 1].
No significant difference between the hearing thresholds on the dominant side compared with the non-dominant side was found.
| Discussion|| |
Mobile phone radiation and health concerns have been raised, especially following the enormous increase in the mobile phone usage throughout the world. They transmit and receive microwave radiations at frequencies of about 900 and 1800 MHz and these frequencies excite the rotations of water and some organic molecules which have been attributed to thermal and non-thermal effects.  The hearing system, particularly the cochlear outer hair cells, is known to be highly sensitive to electric and magnetic fields which produce some hearing sensation. 
The radiation given by mobile phones is measured in terms of specific absorption rate (SAR) which is measured using cellular radiation detectors.  It is a measure of the rate of radiofrequency energy absorption by the body from the cell phone. It provides a means for measuring the radiofrequency exposure characteristics of cell phones to ensure that they are within the safety guidelines. Being nearest to the mobile phone, ear is the most vulnerable organ of the body for high SAR deposition. 
The results in this study are consistent with the results of other studies.
A study showed that a higher degree of hearing loss is associated with long-term exposure to electromagnetic field generated by cellular phones.  Another study showed that subjects who used mobile phones more than 60 min/had hearing threshold of the dominant ears worse than the non-dominant ears.  But there was no significant difference between dominant and non-dominant ears in this study.
| Conclusions|| |
This study revealed that there is a significant increase in the hearing threshold in mobile phone users associated with the duration of usage, but the probable cause of hearing impairment cannot be proved by this study. Further studies with larger population are needed to evaluate the pathophysiology behind increase in hearing threshold in air conduction and bone conduction.
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