Usage of Ear Phones and Subclinical Noise induced Sensorineural Hearing Loss
Authors: Gunavathy Krishnan, Pavithra Saikumar, Karthikkumar Muthukrishnan, Prakash M
Regular use of iPod and MP3 players can lead to irreversible hearing loss. In a study 28% of young college students using iPods were found to have irreversible subclinical sensorineural hearing loss
Sensorineural hearing loss (SNHL) is due to defects either in the sensory end organ of the cochlea or in neural transmission to the central nervous system (CNS). A defect exists either in the conversion of acoustic energy by the sense organ of the inner ear or in the transmission of neural impulses centrally. Noise induced hearing loss is the second most common cause of SNHL after presbycusis. Both the intensity and the duration of noise exposure interact to influence potential damage to the hair cells of the inner ear. No currently known medical or surgical treatments can prevent or reverse noise induced hearing loss.
The advancement in the technology might also be hazardous to the normal functions of the human body. Extensive usage of ear phones can cause irreversible sensorineural hearing loss among people within a decade. Usage of Personal Listening Devices (PLD) like iPods, mp3 Players have increased dramatically. Irrational use of ear phones would have an effect on hearing thresholds.
Chronic noise exposure causes mechanic ultra structurally visible damage at the level of the organ of Corti, initially causing a loss of outer hair cells, leading finally to neuronal degeneration. Typically, hearing loss initially occurs as a sensorineural high frequency notch, normally at 4kHz. The middle frequencies, e.g. the main speech frequencies, are affected considerably later. The extent and progress of the hearing loss depend on the intensity, duration of exposure and frequency composition of the sound and the individual noise susceptibility.
We did a study involving 300 students using ear phones to listen to music using iPods, mp3 players. Questionnaire was designed to survey students about no. of years of ear phone usage, no. of hours per day, model of ear phone used, usage during travel (train, bus). Anyone with the following were excluded from the study. H/O of any ear symptoms, H/O of any otological surgeries,Family H/O of deafness, H/O of exposure to noisy environment, intake of Ototoxic drugs, abnormal Otoscopic finding or Tuning Fork Test (TFT).Out of 300 subjects, 51 were excluded from our study. after obtaining the informed consent from the students the participants were selected based on the duration of ear phone usage, number of hours/day, model of ear phone, volume level etc. They are subjected to otoscopic examination to rule out the external ear pathology, tuning fork tests is done to assess the type of hearing loss and pure tone audiometry test for finding pure tone average. The data has been analyzed statistically.
From PTA readings, average of 500 Hz, 1000 Hz & 4000 Hz was considered to evaluate the subject’s hearing threshold. PTA values - 69 subject out of 249 studied (i.e., 28%) showed minimal subclinical sensorineural hearing loss (SNHL).In subjects with usage of ear phones ≤ 2 yrs significant SNHL was observed among 23% of subjects. In subjects with > 2yrs usage of ear phones the SNHL was found to be 40%.It was noticed that there is a marked increase in SNHL among ear phone users in noisy environment, since they increase the volume of the ear phones in noisy surroundings.
Sensorineural hearing loss (SNHL) is rare in younger age. Sound stress caused by indiscriminate usage of earphones is the most likely cause of SNHL in this age group. This is an irreversible but preventable disability which can be avoided through safety measures. Informing people about the effects of ear phones on the hearing threshold may encourage them to proactively protect themselves.
To conclude prevalence of hearing loss was found to be 28%. It was higher among subjects with, prolonged duration of ear phones usage and listening in noisy environment