Evaluating Auditory Function in Primary School Children with Learning Difficulties in Australia Seong Min (Robyn) Choi BSc, MAudSt, MAudA(CCP), AFHEA A thesis submitted for the degree of Doctor of Philosophy at The University of Queensland in 2019 School of Health and Rehabilitation Sciences 1 Abstract Children who experience poor academic performance at school have been described as having learning difficulties (LD). These children are thought to show reduced performances in reading, written language and numeracy, and to be inactive and inefficient learners. Hearing is one of several factors thought to influence a child’s learning at school with students spending at least 45% of their classroom activities that require listening and 45 to 75% of their time in the classroom comprehending their teachers’ and classmates’ speech. Hearing impairment can include loss of hearing sensitivity and/or impaired auditory processing (AP). While rates of peripheral hearing loss (PHL) in the Australian primary school-aged population is estimated to be between 3.4% and 12.8%, rates of impaired AP in this population are not available in Australia. Children with PHL and/or impaired AP often show behaviours similar to those reported in children with LD, suggesting that LD and hearing impairment could be related in primary school child populations. The present thesis aimed to investigate LD and hearing impairment in a school- aged child population in the greater Brisbane region of Queensland, Australia. The thesis considered two main research questions: (1) Do children with LD have higher rates of impaired hearing and/or impaired AP compared with typically developing (TD) children?; and (2) What models might best explain any relationships between LD and hearing impairment? The first study chapter conducted a systematic review where the rate of PHL in the general primary school child population in Australia was considered. A search of five electronic databases yielded three studies that had quantitatively reported the PH results of screening and follow-up assessment of hearing in primary school children in Australia. The review concluded that the overall rate estimate of PHL in the primary school child population in Australia was between 3.4% and ii 12.8%. The review also compared this rate to other high-income countries and concluded that primary school children in Australia had higher rates of PHL primarily due to higher rates of conductive hearing loss. The second study chapter investigated the rates of impaired hearing and AP in a large, non- clinical sample of children with LD and TD children. A total of 486 children, aged 7.7 to 10.8 years and attending years three and four in six primary schools, were classified as having an LD (n = 67) or being TD (n = 419). This classification was based on a Learning Score generated from their school report results and National Assessment Program – Literacy and Numeracy (NAPLAN) scores. All children attempted a conventional hearing assessment (CHA) involving pure-tone audiometry, tympanometry, acoustic reflexes (AR), and otoacoustic emissions (OAEs). Children returning pure- tone audiometry results within normal limits also attempted an auditory processing assessment (APA) including dichotic digits (DD) and low-pass filtered speech (LPFS) tests. This study’s results showed that, compared to TD children, children with LD were 2.4 times more likely to fail CHA, and 2.1 times more likely to fail APA, and 2.0 times more likely to fail the overall hearing assessment (OHA). In children who had completed the OHA, multiple linear regressions showed average AR thresholds, DD scores and LPFS scores explained 13 to 18% of the variance in the Learning Score. The third study chapter investigated the performance of children with and without LD referred for AP assessment on six tests of AP. Fifty children (aged 7.67 to 10.75 years) referred for AP assessment on the basis of having failed the school-based APD screening tests were classified as having an LD (n = 14) or TD (n = 36) based on the Learning Score. All children completed basic audiometry and an AP assessment consisting DD, LPFS, frequency patterns with linguistic report (FPlin), competing sentences (CS) and two subtests from TAPS-R: Auditory Number Memory – Forward (ANMF) and Auditory Word Memory (AWM). All participants had normal hearing iii thresholds (≤ 15 dB HL from 0.5-4 kHz). Compared to the TD children, children with LD performed significantly worse on FPlinR and FPlinL, DDR, and ANMF. For all children combined, significant correlations were observed between learning score and DDR, FPlinR, FPlinL and ANMF and a multiple linear regression model returned FPlinR DDR and ANMF as significant predictors explaining 50% of the variance in Learning Score. The thesis concludes by reporting that children with LD do have higher rates of impaired hearing and/or impaired AP compared with TD children. Any relationships between LD and hearing impairment might best be explained by risk factor models, association models, and not explained by single distal cause models. The practical implications of these findings for personnel in the health and educations sectors are continued screening for PHL, and a possible expansion of current school- based hearing screening to include AP tests. Future research will need to examine the feasibility of such a screening program, and the possibility of a trans-disciplinary approach to subsequent referral and rehabilitative pathways. iv Declaration by Author This thesis is composed of my original work and contains no material previously published or written by another person except where due reference has been made in the text. I have clearly stated the contribution by others to jointly-authored works that I have included in my thesis. I have clearly stated the contribution of others to my thesis as a whole, including statistical assistance, survey design, data analysis, significant technical procedures, professional editorial advice, financial support and any other original research work used or reported in my thesis. The content of my thesis is the result of work I have carried out since the commencement of my higher degree by research candidature and does not include a substantial part of work that has been submitted to qualify for the award of any other degree or diploma in any university or other tertiary institution. I have clearly stated which parts of my thesis, if any, have been submitted to qualify for another award. I acknowledge that an electronic copy of my thesis must be lodged with the University Library and, subject to the policy and procedures of The University of Queensland, the thesis be made available for research and study in accordance with the Copyright Act 1968 unless a period of embargo has been approved by the Dean of the Graduate School. I acknowledge that the copyright of all material contained in my thesis resides with the copyright holder(s) of that material. Where appropriate I have obtained copyright permission from the copyright holder to reproduce material in this thesis and have sought permission from co-authors for any jointly authored works included in the thesis. v Publications Included In This Thesis Peer-Reviewed Papers Choi SMR, Kei J, Wilson W.J. (2016). Rates of hearing impairment in primary school children in Australia: a systematic review. Speech, Language and Hearing, 1(9), 154 – 162. doi: 10.1080/2050571X.2016.1259199. This paper is incorporated as chapter 4 in this thesis. Contributor State of contribution Choi, S.M.R. (Candidate) Study design (80%) Data collection (100%) Data analysis (100%) Wrote the paper (80%) Edited the paper (70%) Wilson, W.J. Study design (10%) Wrote the paper (10%) Edited the paper (15%) Kei, J. Study design (10%) Wrote the paper (10%) Edited the paper (15%) All authors read and approved the final manuscript. vi Choi S.M.R., Kei J, Wilson WJ. (2019). Hearing and auditory processing abilities in primary school children with learning difficulties. Ear and Hearing.40(3), 700 – 709. doi: 10.1097/AUD.0000000000000652. This paper is incorporated as chapter five in this thesis. Contributor State of contribution Choi, S.M.R. (Candidate) Study design (80%) Data collection (100%) Data analysis (100%) Wrote the paper (80%) Edited the paper (70%) Wilson, W.J. Study design (10%) Wrote the paper (10%) Edited the paper (15%) Kei, J. Study design (10%) Wrote the paper (10%) Edited the paper (15%) All authors read and approved the final manuscript. vii Submitted Manuscripts Included In This Thesis Choi S.M.R., Kei, J, Wilson, W.J. (Under review). Learning difficulties and auditory processing deficits in a clinical sample of primary school-aged children. International Journal of Audiology. This paper is incorporated as chapter 6 in this thesis. Contributor State of contribution Choi, S.M.R. (Candidate) Study design (80%) Data collection (100%) Data analysis (100%) Wrote the paper (80%) Edited the paper (70%) Wilson, W.J. Study design (10%) Wrote the paper (10%) Edited the paper (15%) Kei, J. Study design (10%) Wrote the paper (10%) Edited the paper (15%) All authors read and approved the final manuscript. viii Contributions by Others to the Thesis Significant and substantial inputs were made by others in the research, work and writing represented and/or reported in the thesis. • Associate Professor Wayne Wilson played a major role in all aspects of this research. This included substantial input in the research design, data analysis and interpretation, and critical revisions of written work. • Associate Professor Joseph Kei played a major role in all aspects of this research. This included substantial input in the research design, data analysis and interpretation, and critical revisions of written work. Statement of Parts of the Thesis Submitted to Qualify for the Award of another Degree No works submitted towards another degree have been included in this thesis.