High-Frequency Hearing Loss Amongst Smart Mobile Phone Users: A Case-Control Study.

Over the past 20 years, the number of mobile phone users has surged from 12.4 million to approximately 5.6 billion, representing about 70% of the world's population. Mobile phones can cause headaches, altered sensory perception, sleep disturbances, and a warming sensation around the ear, and devices held close to the ear can potentially damage hearing.

Brainstem Evoked Response Audiometry (BERA) is a non-invasive test that records brainstem potentials in response to click stimuli delivered through headphones. Surface electrodes are placed on the mastoid and the scalp vertex to measure these responses. BERA is used to diagnose defects along the auditory pathway, from the eighth cranial nerve to the auditory cortex.

The purpose of this study was to investigate the effects of smartphone exposure on the central auditory pathway using BERA.

Sixty individuals between the ages of 18 and 30 years were included in the study. Exclusion criteria: Individuals with epilepsy, smokers, those with a history of ear trauma or noise-induced hearing loss, users of neuroleptics, antidepressants, or furosemide, COVID-positive individuals, drug users, and those with chronic conditions such as diabetes, hypertension, arrhythmias, or a family history of hearing disorders were excluded. The participants were divided into two groups: Group I (n = 30): Individuals who had used smartphones for 1-5 years, averaging more than 2 hours per day. Group II (n = 30): Individuals who had used smartphones for more than 5 years, averaging more than 2 hours per day. The hypothesis was that BERA waves and interpeak latency (IPL) would be delayed in individuals with prolonged smartphone use. (IPL refers to the delay between peaks I and III or peaks III and V in the BERA test, typically around 2 ms. Peak I corresponds to the auditory nerve, while peaks III and V represent subsequent brainstem structures, editor's note.) Disk electrodes were placed on the mastoid or earlobe as the active electrode, the reference electrode on the vertex of the skull, and the ground electrode on the midline of the forehead. The right ear was tested, while the opposite ear was masked with 40 dB white noise. Acoustic click stimuli were delivered through headphones at 80 dB at frequencies of 4, 6, and 8 kHz. Two recordings were made to reproduce BERA waves I-VII and the interpeak latencies.

BERA waves III and V were significantly delayed in Group II (> 5 years of smartphone use), indicating potential damage to brainstem structures involved in auditory processing due to electromagnetic exposure. At 4 kHz, significant delays were observed in waves III and V, as well as in the interpeak latencies I-III and I-V. At 6 kHz, significant delays (p < 0.05) were noted in waves III and V, along with highly significant interpeak latency prolongations for I-III and I-V. At 8 kHz, all parameters showed highly significant delays compared to 4 kHz in Group II. The percentage of participants in Group II with delayed BERA waves III and V was: 60% at 4 kHz, 70% at 6 kHz, 83.33% at 8 kHz.

The results suggest that BERA can detect not only the harmful effects of electromagnetic radiation on the hearing of mobile phone users, but also an early involvement of the central nervous system. This effect is particularly pronounced when higher frequencies, such as 8 kHz, are used as auditory stimuli.

These findings are supported by previous research. Philip (2017) reported high-frequency hearing loss in mobile phone users using otoacoustic emissions testing, indicating damage to outer hair cells, especially in the basal turn of the cochlea. Similar trends have been observed by Kothari (2020) and Kellényi (1999). The authors recommend limiting the use of mobile phones for extended periods of time, particularly avoiding holding the phone close to the ear. This may significantly improve physiological and psychological health outcomes in the long term. (AT)