New knowledge on tinnitus gives hope

Text: Maja Lundbäck, first published in the magazine Medicinsk Vetenskap no 2, 2017.

Today, every sixth Swede experiences tinnitus, the perception of sound that do not physically exist. Tones are the most commonly perceived sound, but buzzing, peeping, humming, swishing, droning, whooshing, whistling, or beats that follows the heart rhythms can also be heard. For most people the symptoms are mild, but for about ten percent of those affected, tinnitus is extremely troublesome.

"Not being able to get away from tinnitus often results in clinically significant stress and anxiety. Some people have problems sleeping, with their social life, and difficulties working; the risk of sick leave and disability pension increases,” comments Christopher Cederroth, a researcher at the Department of Physiology and Pharmacology at the Karolinska Institutet.

Every second person with tinnitus also suffers from sound hypersensitivity, which in a mild form makes it more difficult to be present in noisy surroundings or go to a restaurant; in the worst cases it makes each small sound a nightmare.

Tinnitus is still not classified as a disease, but as a symptom of other diseases.

“This is most probably the reason why tinnitus has not received sufficient attention as an important health issue. But I believe that certain forms can be considered as diseases,” says Christopher Cederroth. Many people have experienced “ringing” in their ears after a loud concert. Often the problem has disappeared the next morning. But according to Christopher Cederroth, it isn’t that simple.

“This ringing is a sign that a damage has occurred, and repeated exposure to noise can result in permanent tinnitus. This even applies to music that you listen to at a moderate volume, because it’s also a question of how often you listen,“ he explains.

Christopher Cederroth has himself experienced tinnitus since 2002. He was the bass player in a band for 10 years and stood directly next to the drummer without any hearing protection. “That made my ears more vulnerable. During a New Year’s celebrations, a dynamite stick exploded next to my left ear. Directly after the explosion, a tone started in my ear which I still hear every day,” he says.

The current theory among researchers in the field is that tinnitus occurs when the sensitive nerve cells in the inner ear, generally those that capture the highest frequencies, are damaged. The brain, which is used to receive this sensory input, tries to compensate for the loss of these signals. This results in a type of overactivity in the nerve cells in the brain. In the same way that it is possible to experience sensations from an amputated part of the body, the sensation of sound can be experienced at the same frequency than that at which damage has occurred.

“Animal studies have shown an increased activity in the brain’s auditory centre, but the emotional and cognitive areas of the brain can also contribute to reinforcing tinnitus. If we feel stressed, anxious or think about tinnitus, the activity in the brain’s auditory centre increases and the burden accompanying tinnitus is exacerbated,” explains Christopher Cederroth.

In Sweden, cognitive behavioural therapy, CBT, is recommended, which can make it easier for people to manage their symptoms; however, psychotherapy does not actually silence the tinnitus. It is difficult to find good treatments, and only small resources are allocated to research. Moreover, it takes time to introduce effective methods that are available in Sweden.

“This is a shame, because several treatment options are supported by evidence,” comments Christopher Cederroth.

Cochlear implants, which stimulate the auditory nerve in the inner ear using weak electrical impulses, have been shown to remove tinnitus in people with hearing loss. Another method that is used in Germany is a form of sound therapy, called “Notch music therapy”. This uses special telephone applications or hearing aids which filter out the sounds in the range close to the tone experienced with the tinnitus. Notch music therapy can be used with people who experience a tone in the ear. Unfortunately, as there are so many variants of tinnitus, there are still many people who do not get help. The US, Germany and the Netherlands have national guidelines for the treatment of tinnitus. Christopher Cederroth believes these are also necessary in Sweden.

Thousands of patients are severely affected each year, incurring high costs for society.

That the environment has a major effect on the problem, there is no doubt. The risk of being affected by tinnitus is greatest in metropolitan areas and increases with age. In Stockholm, every third person over 60 is affected and, according to Christopher Cederroth, the problem will be increasing in line with our modern lifestyle with a lot of sound and noise pollution.

“Many people listen in their earphones in a noisy background at high volume even though the phone alerts you with a red colour if the sound exceeds 85 decibels. This is not good, and even more if you are young,” he says.

Whether you develop tinnitus appears to depend on a combination of how high, how often, and for how long you are exposed to sound. There also appear to be differences in how predisposed you are to being affected. Christopher Cederroth and his colleagues recently published a study which showed that genetics can sometimes be more important than the environment. Using the Swedish Twin Registry, the researchers could see that tinnitus in both ears, so-called bilateral tinnitus, show high heritability, at least in men. This discovery makes it possible to have a better understanding of how tinnitus occurs.

“Through our discovery, I hope that we will be able to develop an effective drug against tinnitus. But we also know that tinnitus is sustained and enhanced by thoughts and emotions. I therefore believe that, in order to provide optimal treatment, we must look at tinnitus from an interdisciplinary perspective, and consider tackling the problem from several angles at the same time,” he concludes.