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Standing Committee on Health, Aged Care and Sport
14/02/2017
Hearing health and wellbeing in Australia

HUNTER, Dr Matthew, Member, Human Genetics Society of Australasia

Evidence was taken via teleconference—

[12:19]

CHAIR: Firstly, can I check: do you have any objection to being recorded by media during participation in this hearing?

Dr Hunter : No, I have no objection.

CHAIR: I need to advise you that these hearings are formal proceedings of the parliament. The giving of false or misleading evidence is a serious matter and may be regarded as a contempt of the parliament. The evidence given today will be recorded by Hansard and attracts parliamentary privilege.

As I think you might know, this is the first of the public hearings that we are holding in relation to our inquiry on hearing loss and hearing health. As this is the start of the process, we thought it would be useful for the committee members to basically get an overview of the causes and treatment, and future treatment options, available to people with hearing loss. Some of our questions will follow that line of inquiry.

I wanted to see if you might like to make a short opening statement before we get underway.

Dr Hunter : I would like to make an introductory statement if that is possible. Just to give you a bit of background about myself, I am a clinical geneticist, which means that I see patients affected by genetic conditions, and I am a specialist from paediatrics. I have been a doctor for 21 years now and have worked in clinical genetics for 10 years, and of those 10 years I have been working in deafness for about seven years. We operate a genetics of deafness clinic at Monash Medical Centre in Melbourne.

To tell you a little about the genetics of hearing loss, which is my field: hearing loss, as you would be well aware, is a prevalent condition worldwide. It affects about three in 1,000 children, that is, present from birth, but it affects a staggering 50 per cent or so of people 75 years of age or older with age-related hearing impairment, or presbycusis.

What we know about the congenital forms of hearing loss, that is, from birth, is that approximately 50 per cent is genetic and then a further 25 per cent is not genetic, where cytomegalovirus is a major cause here, and then for the remaining 25 per cent we have not established what the cause is yet.

Looking at age-related hearing impairment, this is a complex disorder and it is multi-factorial, meaning that there are likely to be environmental and genetic factors combining in that person to create that susceptibility and development of age-related hearing impairment. It is more common in men than women and noise exposure is a major environmental factor contributing, but increasingly we are understanding that there are susceptibility genes which predispose a person to developing age-related hearing loss or susceptibility to noise-induced hearing loss.

Of the known causes of genetic hearing loss, particularly in children, we know that 70 per cent are non-syndromic, in other words, there are no additional medical features or symptoms, and about 30 per cent are syndromic, where there are other features. The majority of non-syndromic hearing loss falls into a pattern of inheritance called autosomal recessive inheritance, so about 80 per cent of non-syndromic hearing loss is recessive. Autosomal dominant inheritance is the next most common pattern, at about 15 per cent. So that is non-syndromic hearing loss. If you look at syndromic hearing loss, there is a myriad of syndromes associated with deafness; over 400 at the last count. Of those, there four reasonably common ones that make up the bulk of that, which are Usher syndrome, Pendred syndrome, Waardenburg syndrome and Branchio-oto-renal syndrome.

That is just a bit of background about hearing loss. I will briefly touch on genetic testing and therapies, as I am sure you will be interested in those. There have been some major advances recently in genetic testing—in particular in a technology called next-generation sequencing. This allows for rapid screening of all of the known non-syndromic genes, or syndromic genes, in a single test, depending on how you have designed your test. Of particular significance is that most genetic testing in Australia is not funded by Medicare, so many patients in our clinics have to self-fund their testing unless we provide funding for that based on it altering management or treatment or being used for reproductive decision making. However, I must also say here that the position of the HGSA is that hearing loss is one of many thousands of genetic conditions and that the feeling of the HGSA is that all genetic conditions should be funded equally, if funding were something that this committee were going to be deciding on.

With regard to therapies for the treatment of deafness, this committee would have heard of hearing aids and very likely cochlear implants as well, but you may not be aware of recent advances in the molecular understanding of specific genes and conditions which mean that new medications which are coming through and currently being tested in animals are able to restore hearing in the context of noise-induced or age-related types of hearing loss after hearing has already been lost, which is quite phenomenal. But I think we are a long way off it being available in humans, because human trials take so long. Similarly, genetic therapies or gene therapy is also being developed concurrently, which allows the correction of a gene mutation either in stem cells for transplantation or actually in the organism itself—a living mouse, for instance, where a vector is given and is able to correct the genetic defect in the cells that it needs to be corrected in.

That is just a little brief background. Are there any questions about that?

CHAIR: Thank you, Dr Hunter. I might just start off with three questions. It is reasonably freewheeling, so we will go backwards and forwards between committee members a little bit in the time we have available. I just have three quick questions. Firstly, in relation to genetic testing, are Medicare rebates available currently for any genetic testing in Australia?

Dr Hunter : Yes, there are a handful of genetic tests that do attract a Medicare rebate, but the vast majority of conditions and genes are not covered by that.

CHAIR: Do you happen to know what type of genetic testing does attract a rebate at the moment?

Dr Hunter : Yes. I do not have a comprehensive list here for you, but I can give you some examples. For instance, chromosomal analysis does attract a rebate, as do certain specific genes like, for instance, fragile X syndrome and myotonic dystrophy, to name a couple of conditions. But I can provide the committee with a complete list if you are interested in that.

CHAIR: That would be great if you could. That would be fantastic. My second question was: you concluded by mentioning the development of new medications. I was just interested in where the centre of research activity is globally for those new medications, if there is such a thing. For example, are some of those being developed in Australia, or is it predominantly occurring elsewhere?

Dr Hunter : It is predominantly occurring elsewhere, just because the research dollars in the US and Europe seem to be greater, but Australia certainly has contributed significantly to research in this area in the development of cochlear implants, which we are world renowned for.

CHAIR: My final question was just in relation to age related hearing loss. Is that something that every individual will experience to some degree, or are there some people that will get to 100 without any hearing loss?

Dr Hunter : We know some people are protected against it and we do not know what those protective factors are yet, and other people are predisposed to it. With minimal noise exposure or other exposures, such as to medications or other toxic substances, they will develop what appears to be age related hearing impairment, but it is probably a combination of noise exposure and then genetic susceptibility.

Mr GEORGANAS: Dr Hunter, you spoke to us about the percentages of people being identified with genetic hearing through illnesses et cetera. How common is genetic hearing impairment across the board, in terms of being identified in the population?

Dr Hunter : The standard dogma on that is that approximately 50 per cent is genetic and 25 per cent is non-genetic, but that 25 per cent still to be established could be either genetic or environmental or a combination.

Mr GEORGANAS: Out of genetic conditions in children being born with hearing impairment, is that confined to the inner ear? When you have a genetic condition, is it confined to a particular part of the ear? Are some parts more susceptible to genetic conditions?

Dr Hunter : What we know is that probably the majority of that is sensorineural hearing loss. In other words, it is either related to their hair cells or the nerves that are important in the inner ear. But we do know that there are other types of hearing loss—in particular, conductive hearing loss where there is a conduction defect from the outside related to the ear canal or the eardrum or the bones that conduct that sound from the eardrum to the inner ear.

Mr GEORGANAS: My last question might sound pretty plain, but how do we identify genetic loss?

Dr Hunter : It is actually a very good question, because that is what we have been grappling with for decades until fairly recently. We know the majority will be genetic so we always go into a diagnostic process with that assumption. What we will do is rule out the common environmental causes, such as cytomegalovirus, but then we get to a point where we have to initiate genetic testing to then take the next step.

We tend to start with the most common single gene cause of deafness, which is connexin 26. That accounts for quite a large percentage—about 15 to 18 per cent of deafness is due to the single gene. After that, if we have not found the cause, we either have to recognise the syndrome clinically and see other symptoms or we have to go on and test for non-syndromic hearing loss. The only way to do that, really, is to do a gene panel and test all of the other known genes, which, as I have said, has only recently become available with next-generation sequencing.

Mr DRUM: Is there a significant issue that you would encourage the committee to investigate or is there a part of hearing health that you would like the committee to specifically focus on?

Dr Hunter : I do not really know what the terms of reference of your committee are so, purely from a perspective of working in the field, the area that I think is important and the committee should potentially take note of is that age related hearing loss is incredibly common. It is getting more common with an ageing population and we still do not have treatment for that, but I think those are coming through the pipeline. Looking at how one manages that, treats that and gets those treatments onto Medicare in an expeditious fashion would be a very sensible thing to do. With regard to childhood onset hearing loss, either congenital from birth or in early childhood, again, diagnosis is a big factor. The funding of genetic testing for children, so that we can know with confidence that it is genetic and then work out whether there are various specific treatments or not, would also be very helpful; although treatments are likely to take a little while until they become available, so there is time for that kind of funding, I think. Does that answer your question?

Mr DRUM: Yes. Thank you very much.

CHAIR: What is the feeling about the rates of genetic hearing loss, particularly at childbirth. Is it regarded as rising or falling in Australia?

Dr Hunter : My understanding is that it is static. The statistics that I have seen look like it is pretty stable, although there are some ascertainment issues. If you go back, say, 50 years the number of people who would have been ascertained with mild hearing loss would have been quite low whereas now we are much better at picking them up with a newborn infant screening programs, which has made a big difference to early detection and therefore the ability to help these children, from an educational perspective, with hearing aids or cochlears.

CHAIR: You alluded to this in your answer to Mr Drum: is identifying the precise genetic cause of hearing loss currently relevant to treatment?

Dr Hunter : Yes, it is—and it is very relevant. If you look at a family that has had one deaf child and they want to have more children, sometimes they will hold off on having children or will not have more children because of the fear of that. Secondly, sometimes they go ahead anyway and have a second child, when they are the kind of family that does not think too deeply about this. There are already reproductive technologies, such as IVF and embryo selection, which allow us to prevent that condition being inherited in a second child or more than two children in the family. That is already available, and we do that kind of testing on a regular basis.

But in addition to that we are also starting to learn that some specific types of hearing loss, whose genetic basis one does need to identify, can be treated or have specific management recommendations. So while we may not be able to cure them we can actually prevent deterioration, or we have surveillance programs to look for other features which are common in the particular condition. So, yes, it does make a difference knowing the genetic cause.

CHAIR: Right. Dr Hunter, I think that is the conclusion of our questions. Thank you for your participation today. I think it has been really useful for the committee's inquiry and for those of the committee who could be here today. Thank you also for agreeing to provide that list of genetic tests for which there is a Medicare rebate. If you could forward that through to our committee secretariat by 21 February that would be wonderful.

Dr Hunter : It would be my pleasure.

CHAIR: If we have any additional questions then obviously we will communicate those to you through the committee secretariat.

Dr Hunter : I am happy to be contacted by email or by phone for any questions that you have.

CHAIR: We also have Hansard transcript of the session, which the committee and the secretary will provide you with a copy of as well.

Dr Hunter : Great. If I find out that there are any errors in that, should I then contact the committee?

CHAIR: That is correct.

Dr Hunter : Right. I will do that.

CHAIR: Wonderful. Thanks, Dr Hunter.

Dr Hunter : Have a good day.

CHAIR: We have no other witnesses today, so I declare this public hearing closed.

Committee adjourned at 12:38