Have you ever had a ringing in your ears that only you can hear, especially after you have been exposed to a loud noise? Some people describe it as chirping, whistling, buzzing or hissing. There is actually a medical term for that – Tinnitus.
The term is used to describe the perception of sound that has no source externally. Cochlear hair cells that are located in the inner ear contract and stretch repeatedly in response to vibrations such as those induced by sound. When these hair cells are damaged (temporarily or permanently), the condition is diagnosed as Tinnitus. The damage is caused when the cochlear hair cells are overloaded by very loud noise, such as fireworks, live pop music, explosions or listening to music through ear buds with the volume cranked up high.
While it was previously believed that tinnitus is a problem of older people, a recent study performed in Brazil by Tanit Ganz Sanchez, associate professor of otolaryngology at the University of São Paulo’s Medical School (FM-USP), found a very high occurrence of tinnitus among adolescents. In addition to listening to music using ear buds for long periods daily teenagers often visit very noisy places like discos, rock concerts and nightclubs.
Sanchez warns that this generation will probably suffer from severe hearing loss by the time they are 30 or 40 if they continue to be exposed to very high noise levels. In the study, teenagers were asked to complete a questionnaire stating whether they had experienced tinnitus in the previous 12 months. If this was the case, they were asked to detail specifics such as the frequency, duration and volume of the incident. An otoscope was used to examine the ears of 170 students between the ages of 11 and 17 and of these, more than half (54.7%), reported they had experienced tinnitus in the preceding year.
Sanchez finds this level of prevalence alarming, and notes that it affects even younger groups, including children. The group who had reported prior tinnitus (54.8% of this group) said they had noticed it after listening to loud music. They were then given a psychoacoustic examination to measure hearing function. The tests, carried out in an acoustic chamber and administered by an audiologist, made use of an audiometer at 14 frequencies (0.25-16 kHz). Apart from measuring hearing function, the test measured the intensity of any tinnitus experienced together with the level of loudness discomfort.
The results obtained from these tests were comparable to those found in adults with chronic tinnitus and tinnitus was perceived in the acoustic booth by 28.8% of the total sample.
What is worrying is that tinnitus is an early sign that appears well before any actual hearing loss. Although adolescents perceive tinnitus very often, they seldom complain about it and visits to a doctor or hearing specialist is even rarer. Sanchez warns that without treatment, the problem can become chronic at a much earlier age. As the teenagers are unaware of the dangers associated with tinnitus, they are also unlikely to reduce their exposure to the very noisy and damaging environments.
When cochlear hair cells are damaged or dead, the loss of function is compensated for by neighboring regions of the inner ear working faster and harder, giving rise to tinnitus. Neuroscientists recently conducting animal experiments do however suggest that this is not the only cause of tinnitus. If the hair cell synapses (neural pathways) from the hair to the cochlear nerve is impaired, this could lead to a reduction in the neural output from the ear to the brain. This could reduce a teenagers sound level tolerance in addition to only hearing loss. Sanchez admits that the results of his study could be skewed in that it may be a sign of damage to hair cell synapses rather cochlear hair cells being damaged. If this were the case, it wouldn’t be detected by an audiometric examination and it would appear that there is no damage to the auditory pathway, making diagnosis difficult.
The bottom line is that teenagers that continue to frequently expose themselves to very noisy environments until the age 20 or 25, may become deaf while still relatively young.
Study has been published in the journal Scientific Reports.