Mobile phones and MP3 players-devices that many of us now can't live without-have been linked to tinnitus in two recently published studies, thereby suggesting a possible explanation for the growing prevalence of the disorder over the past 10 years. Currently, around 10-15 per cent of people in the developed world suffer from the condition.
One of the studies-a look at mobile phone use in relation to tinnitus-was carried out by a team of researchers from the Institute of Environmental Health at the Medical University of Vienna, in Austria.
The team compared 100 consecutive patients who required treatment for chronic tinnitus-defined as lasting for at least three months-with 100 randomly selected people without the disorder, but matched for age and gender, for a period of one year. Anyone who had an ear disorder, noise-induced hearing loss, high blood pressure or was taking certain medications was excluded from the study, as these factors are known to increase the risk of tinnitus and could, therefore, influence the results.
After analyzing the data for participants' mobile-phone use up to the onset of tinnitus symptoms, the researchers found that those reporting prolonged use of a mobile phone (four years or more) had a significantly greater risk of tinnitus-and, in particular, on the same side of the head as they used the phone.
Moderate increases in risk were noted for all indicators of intensity of phone use (average daily duration of use for 10 minutes or more, cumulative hours of use of 160 or more and cumulative number of calls in excess of 4000), but the results were not statistically significant. The researchers believed that this was because the size of the study population was not large enough to detect less-pronounced risks.
Still, the team concluded that "high intensity and long duration of mobile phone use might be associated with tinnitus".
Although this was a small study with a number of draw-backs (it's likely that people may have over- or underestimated their mobile phone use, for example), the researchers caution that "it is unlikely that the increased risk of tinnitus from prolonged mobile phone use in this study is spurious".
Given the high prevalence of tinnitus and the nearly ubiquitous use of mobile phones, even a slightly increased risk would be of public-health importance, they said.
Moreover, there is a plausible explanation for the possible link between mobile phones and tinnitus, as the cochlea and auditory pathway both directly absorb a considerable amount of the microwave energy emitted by a mobile. The electromag-netic radiation could be causing a "calcium imbalance in the neural acoustic pathway and also activation of nitric oxide synthase", the researchers pro-posed, and this may be involved in the development of tinnitus (Occup Environ Med, 2010; 67: 804-8).
The MP3 player linkup
The other study to find a connection between audio technology and tinnitus was an investigation into the potential risk to hearing associated with the use of portable digital players, more commonly known as MP3 players.
In this study, scientists at the University of Ottawa in Canada evaluated 28 university students, aged between 17 and 23, who completed a 49-item questionnaire on their listening habits and hearing health.
Among other things, the questionnaire assessed how often and for how long the students listened to their MP3 players, and at what typical volume settings, as well as how many of them experienced tinnitus (defined as ringing, rushing or buzzing sounds in the ear for which no other cause can be found) either generally or specifically after listening to their players.
The results showed that, on average, the students listened to MP3 players for 2 hours a day, 6.5 days a week, and half of them reported using their devices (with earphones) every single day.
What's more, the researchers discovered "significant differences" in MP3-player listening habits between respondents who had experienced tinnitus and those who had not, thus suggesting a possible link between the two.
Altogether, 10 of the 28 students reported experiencing tinnitus, with seven of the 28 (25 per cent) saying they experienced it after listening
to their MP3 player. An analysis of the data for these seven students revealed that, com-pared with those who had not experienced tinnitus, they had generally been using an MP3 player for a greater number of years, and tended to listen at louder levels.
On average, tinnitus sufferers had been using MP3 players for 1.5 years longer than the non-sufferers (5.5 years vs 4 years), and listened at a typical volume setting that was 12 decibels louder (78 decibels compared with 66)-a difference that was statistically significant. A significant difference was also found when 'worst-case' sound levels were analyzed-in other words, the loudest volume the students reported using (as might arise, for example, in a noisy environ-ment such as the gym or on a bus). Those reporting tinnitus had slightly higher levels (82 decibels) compared with those not reporting tinnitus (75 deci-bels)-a difference of 7 decibels (J Acoust Soc Am, 2010; 128: 646-53).
However, yet again, further research is needed to confirm these findings, particularly as this was such a small sample population, but the results certainly make sense. Indeed, according to the American Tinnitus Association (ATA; www.ata.org), overexposure to loud sound is the leading cause of tinnitus.
MP3 players are only one way in which we are exposed to loud noises, but their huge pop-ularity, especially among young people, makes them a particular cause for concern. Indeed, a recent editorial by Peter Rabinowitz, from the Yale Occupational and Environ-mental Medicine Program in New Haven, CT, reports that more than 90 per cent of young people in Europe and the US use personal music players-often listening for several hours a day at maximum volume (BMJ, 2010; 340: c1261).
Whether the rapid rise in MP3 players in recent years has anything to do with the rising rates of tinnitus remains to be ascertained, but it may well be that many people are at an increased risk of the condition if they listen to too-loud music for too long.
The best general advice is to turn down the volume and take regular breaks from listening. As a rule of thumb, if the music is uncomfortable for you to listen to, or if you can't hear any external sounds when you've got your headphones on, then the volume is too high. (For more information on how noise affects hearing and how to protect yourself, see WDDTY vol 21 no 8.)
Likewise, more research is needed to determine whether or not mobile phones have a role to play in tinnitus. But, in any case, considering the other mobile-related risks to health (see WDDTY vol 20 no 9), it may be best to keep your calls to a minimum.
Factfile: Treating tinnitus
Tinnitus can be caused by certain drugs (see box, page 28) and a variety of health conditions-ranging from blood vessel disorders to ear-wax buildup-so identifying and treating the underlying cause may well resolve the problem. However, in most cases, there seems to be no cure for chronic tinnitus, so treatment focuses on making the problem more manageable. Studies have shown that the following may be helpful.
u Sound therapy involves the use of external noise to distract the sufferer from the persistent sounds of tinnitus. For example, bedside sound generators, which produce pleasant music or background noises, have been reported to improve sleep in tinnitus sufferers (Acta Otolaryngol Suppl, 2006; 556: 59-63). Acoustic stimuli delivered through hearing aids can also provide relief (J Am Acad Audiol, 2010; 21: 461-73). Avoid exposure to loud sounds, however, as they may make tinnitus worse.
u Tinnitus Retraining Therapy (TRT), a combination of sound therapy and educational counselling, aims to train the brain to ignore the sounds of tinnitus. One review of the literature so far suggests that TRT is more effective for tinnitus than sound therapy alone (Cochrane Database Syst Rev, 2010; 3: CD007330).
u Transcranial magnetic stimulation (TMS) is a non-invasive procedure that uses magnetic fields to stimulate nerve cells in the brain. In one small double-blind trial, patients who were given TMS for five days showed a significant reduction in tinnitus complaints compared with those who received a sham treatment-and the results lasted for at least six months (Eur J Neurol, 2010; 17: 38-44).
u Hypnotherapy may be helpful for tinnitus sufferers, according to the evidence so far, which is considered poor. However, although well-designed, controlled trials are lacking, hypnosis practitioners commonly report a success rate of 70 per cent (Int Tinnitus J, 2008; 14: 135-8).
u Qigong, the traditional Chinese technique that combines slow gentle movements with meditation and breath regulation, was recently found to improve tinnitus in a randomized controlled trial. In 80 patients with tinnitus of at least three months' duration, regular qigong practice (10 sessions over five weeks) dramatically reduced the severity of the condition, and the effects lasted for at least three months after stopping the practice (J Psychosom Res, 2010; 69: 299-304). It may work by reducing stress, which has recently been linked to tinnitus (BMC Public Health, 2011; 11: 130).
u Nutritional supplements may help tinnitus, including:
v antioxidants. In an uncontrolled study of 31 patients with tinnitus, 18 weeks of oral antioxidant therapy, including beta-carotene, and vitamins C and E, reduced the intensity of tinnitus and the discomfort experienced by the sufferers (Arch Med Res, 2007; 38: 456-9).
v Ginkgo biloba. Several studies suggest that a standardized Ginkgo extract (120 mg/day), containing 24-per-cent flavone glycosides and 6-per-cent terpene lactones, may be effective for tinnitus relief (Fortschr Med Orig, 2001; 118: 157-64).
v zinc. A review of the literature suggests that tinnitus sufferers, particularly the elderly, tend to be deficient in zinc, and that supplementation could be beneficial in many cases (Prog Brain Res, 2007; 166: 279-85). One study reported that supplementing with zinc in patients who were marginally zinc-deficient improved tinnitus and hearing loss in about one-third of the elderly (Am J Otol, 1989; 10: 156-60).
Factfile: Tinnitus-causing drugs
u Non-steroidal anti-inflammatory drugs (NSAIDs), such as aspirin
u Chemotherapy drugs, such as cisplatin and carboplatin
u Antibiotics, such as aminoglycosides
u Antimalarials, such as chloroquine
u Loop diuretics, such as furosemide.
WDDTY VOL. 22 NO. 1