All participants were taken up for several audiologic investigations including pure-tone audiometry, speech discrimination score, speech reception threshold, impedance audiometry, distortion product otoacoustic emissions (DPOAE), auditory brainstem response (ABR) and middle latency response tests.
Chronic use was defined as using a mobile phone for more than 1 year.
|Reference group 1||nonusers of mobile phones: controls|
|Group 2||GSM users|
|Group 3||CDMA users|
|Group 4||GSM users, cumulative use: < 3 years|
|Group 5||GSM users, cumulative use: > 3 years|
|Group 6||CDMA users, cumulative use: < 3 years|
|Group 7||CDMA users, cumulative use: > 3 years|
GSM and CDMA mobile phone users were found to be at a significantly higher risk of having distortion product otoacoustic emissions (DPOAE) absent as compared with controls. They were found to have higher speech frequency thresholds and lower Na and Pa amplitudes of the middle latency response. Increased changes in the auditory parameters were observed in participants who used their mobile phones more than 3 years compared to persons who used their mobile phone less than 3 years. The damage done was bilateral, with the quantum of damage being the same for both GSM and CDMA.
The authors conclude that long-term and intensive GSM and CDMA mobile phone use might cause damage to cochlea as well as the auditory cortex.