European researchers identify genetic determinants of deafness

September 1 is World Deafness Day

Deafness is a real and often underestimated health problem in Europe: 6% of the European population suffer of hearing impairment. It is now known that over 50% of all hearing impairments is caused by genetic factor. Over the last 7 years, the European Commission has channelled more than €10 million into research on different aspects of deafness. One particular project receiving support from the European Commission identified several genes which when affected lead to inherited deafness in humans. These discoveries increase significantly our understanding of the hearing process and open avenues for new therapies for deafness.

On the occasion of World Deafness Day on 1 September, European Research Commissioner Philippe Busquin said: “The number of patients suffering of hearing impairment is constantly growing due to increased noise pollution and to an ageing population. So far, aside from hearing aids, there is no remedy for deafness. Developing new therapies requires the best researchers from different countries and disciplines to work together in order to improve our knowledge on the hearing process and to identify the causes leading to deafness. This is precisely what the EU is making to happen through its research programmes.”

Deafness is a real heath problem in Europe

In Europe, 22.5 million individuals suffer form hearing impairment with 2 million profoundly deaf. In children, deafness impedes language acquisition and generates learning difficulties. In adults, if often leads to severe disruption of social links which very frequently results in depression. All together, in Europe, the financial cost of hearing impairment has been estimated to be €78 billion per year (based on average of €3,500 per patient annual costs for special education, speech therapy, hearing aids, physician and specialists fees, and other expenses). This is more than the combined economic costs of epilepsy, multiple sclerosis, spinal injury, stroke and Parkinson’s disease. Furthermore, this figure is likely to grow continuously in time due to noise pollution and ageing. Hearing loss is the third leading chronic disability following arthritis and hypertension.

Research on deafness is a European priority

The European Commission is supporting research on deafness for many years. In particular, the project “hereditary deafness” co-ordinated by Prof. Christine Petit (Pasteur Institute, Paris, France) allowed substantial progress in the understanding of the hearing process and in the identification of the genetic determinants of deafness. 50 % of the hearing deficiencies have a genetic origin. Importantly, this consortium of leading European researchers identified half of the 36 genes known to be associated with deafness. One of these genes, “connexin 26” was found to be responsible for more than 30% of deafness cases in Europe. The identification of the genetic determinants is crucial for diagnosing the underlying causes of deafness. These diagnostic tools are now available and can be used in a very large proportion of cases of deafness to identify the genetic origin of their hearing impairment.

Furthermore, this research has considerably increased our knowledge of the hearing mechanism: i.e. how a wave sound can be transmitted from the outer ear to the inner ear and be sent to the brain as an electrical signal. These discoveries open new avenues for developing innovative therapies for deafness. Several mouse models have also been developed mimicking the human hearing impairments. They will be very useful for testing new therapeutic approaches.

All together, this European effort has considerably increased our knowledge on this important health problem. However, we are still far from understanding the complete picture and most importantly there is still a long way before having new potential therapies for deafness. This is why the European Commission has made deafness a research priority in the second call for proposals of the Sixth Framework Programme published in July 2003, inviting large European projects to study the hearing process and deafness.