Evaluating auditory function in primary school children with learning difficulties in Australia

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 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 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.