The "LOCHI" study, as it is most commonly known, aims to examine the longitudinal development of children who have been identified with hearing loss in New South Wales, Victoria and Queensland. The first phase focuses on development up to 5 years of age with the second phase testing children up to 9 years of age.
Approximately 468 children are participating in the LOCHI study in QLD (21%), NSW (51%) and VIC (28%). Male participants make up 54% of the study and 25% of participating children have additional disabilities. Type of hearing loss is divided up as follows:
Informed consent has been gained from all participating families. Contact details of named members of the research team have been provided to families and researchers are able to be contacted freely to discuss and answer questions. Participation in this study is voluntary and parents are able to withdraw their child at any stage without explanation and consequence on the services they receive from Australian Hearing and intervention centres. Families are also provided with contact details of the Secretary of the Australian Hearing Human Research Ethics Committee if they have concerns about any ethical aspect of this research.
Children in the study are assessed at the following intervals:
Families will be contacted by a member of the LOCHI team close to their upcoming assessment date and a suitable time for the assessment to take place will be worked out. Assessments usually take around 3- 4 hours and include hearing and language assessments that are carried out over a couple of sessions. They take place at the hearing centre, early intervention centre where a child normally receives services or at their school. During a visit, the child’s ability to communicate verbally, to perform tasks according to verbal instructions and to repeat what’s heard will be assessed. In addition, parents/caregivers and teachers will be asked to complete questionnaires and to provide verbal reports on their children’s behaviour in real life. If the parent/teacher is not present at the assessment, questionnaires will be posted out. An assessment of non-verbal general ability will also be administered to the child after he/she turns 5 years of age.
Normative data sub-study
An essential part of the LOCHI study is to relate how children with hearing loss perform on the tests when compared to children who have normal hearing. Some of the tests that we use do not have normal comparison data and some tests were produced and normed in America. It is important then for us to know how Australian children with normal hearing perform on these tests. For these reasons, we have a sub study running at the same time as LOCHI, testing children with normal hearing on the LOCHI test battery. The same team of researchers that test children on the LOCHI study conduct the sub study assessments so that we can ensure that the tests were administered exactly the same way. We are recruiting children who match the LOCHI children in age, gender and socio-economic status. Some of the children we have tested so far have been siblings, cousins, friends or classmates of children participating in LOCHI.
At the moment we are recruiting children at the ages of 5 years and 9 years in Queensland, New South Wales and Victoria. The children are provided with a hearing screening conducted by an Audiologist and a comprehensive battery of speech, language and educational assessments conducted by a Speech Pathologist. Two assessment sessions of approximately one hour are required. The assessments take place in schools, kindergartens, at home, or at hearing centres, just like the LOCHI assessments. Generally it would cost between $250-$500 to access this type of testing privately however we provide the assessments free of charge.
If you know someone who might be interested in participating in this study, please ask them to contact the researcher in your state
Victoria – Julia Day 0383259014 or Laura.Button@hearing.com
Queensland – Louise Martin 0732376841 Louise.Martin@hearing.com.au
New South Wales – Vivienne Marnane 0294126972 Vivienne.Marnane@ nal.gov.au
Frequency Compression sub-study
Frequency compression maps high-frequency sounds to an adjacent lower frequency region where hearing loss is less severe. This study aims to determine the effect of frequency compression on speech production, speech perception, real-life performance and quality of life for young children with different degrees of hearing loss.
Genetics sub-study results
Hearing losses are caused by genetic (inherited) factors, environmental factors or a combination of both. Genetic factors are changes in the genes that we have inherited from our parents. In 60-70% of children and young people with a hearing impairment the underlying cause is genetic.
Our chromosomes contain the DNA that encodes our genes, of which there are approximately 25.000. We usually have two copies of each gene: one copy inherited from our mother, the other inherited from our father. The gene products, usually proteins, control and regulate functions in our bodies. The ear is a complex organ and the hearing process intricate, and it is therefore not surprising that many genes are involved in hearing. If one or more of these genes does not function normally, the consequence could be a hearing loss. It has been estimated that there is more than different 200 genes that can cause deafness. A change (mutation) in one of these genes might affect its function and thereby cause a hearing impairment.
It was not possible for us to analyse all the genes associated with hearing loss, so we focussed on the most common genetic causes of deafness: the connexin 26 gene (Cx26, GJB2), the pendrin gene (SLC26A4), and a change in the mitochondrial DNA, the A1555G mutation. We also investigated a common environmental cause of hearing loss: cytomegalovirus (CMV) infection.
The tests were done on blood spots (Guthrie cards) collected shortly after birth. We screened blood spots from 368 children and found:
49 children had two known connexin 26 gene mutations
35 children had one known connexin 26 gene mutation
1 child had a change in connexin 26 gene of unknown consequence
7 children had two known pendrin gene mutations
19 carried one known pendrin gene mutation
3 children had single changes in the pendrin gene of unknown consequences
1 child was positive for the mitochondrial DNA A1555G mutation
CMV DNA was detected in 28 of 368 children
The results show that mutations in the connexin 26 and pendrin genes, as well as congenital CMV infection, are relatively frequent causes of hearing loss in Australian children. These results are similar to those found in similar studies overseas. However, the A1555G mitochondrial DNA was only detected in one child and does not appear to be common in the general Australian population.
Having two known mutations in the connexin 26 or pendrin genes explains these children’s hearing loss. There are 54 children with only one known mutation in their connexin 26 or pendrin genes. Mutations in these genes are recessive, which means that in order to have a hearing loss the person should have mutations in both copies of the gene. People with mutations in only one copy of these genes usually have normal hearing. Because of the numbers, we believe that the single mutations found in the 54 children contribute to their hearing losses, but we are still unable to explain why these children have a hearing loss, when we would expect them to be unaffected. There must be other genetic or environmental factors that play a role in the hearing loss - factors that we still haven’t identified.
The Guthrie blood spots were used for CMV screening because these are the only DNA source available from the time of birth of the children. However, it was recently shown that the use of Guthrie blood spot DNA in CMV testing often give a negative result, even if there has been a CMV infection during the pregnancy. This is because the CMV DNA in the blood spot is below detection limit or not present. Our finding that 8% of blood spots were CMV positive is therefore likely to be an underestimation of the true number of newborn hearing impaired Australian children with a congenital CMV infection. On the other hand, not all children with a congenital CMV infection develop a hearing loss, so we cannot be absolutely certain that the deafness in a CMV positive child is due to the viral infection.
This study presents the first comprehensive analysis of the most common causes of hearing loss in Australian children. It provides a basis for further studies aimed at determining the impact of connexin 26 and pendrin gene mutations and congenital CMV infection on speech, language, and psycho-social outcomes in children with hearing loss.
We thank the families who participated in this study for their help and understanding.
Confidentiality: How your information is protected
Confidentiality of all data is protected by use of identifying codes. All paper records are kept in locked cabinets and accessible only to authorised project staff. Electronic records are stored on a server (which is not accessible from outside NAL premises) in a directory that is password-protected from all individuals that are not part of the project. No individual is identifiable in reports or software that arises from the study.