A Danish cohort study

International Journal of Pediatric Otorhinolaryngology 90 (2016) 91e98

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Associations between childhood hearing loss and behavioural and academic difficulties: A Danish cohort study Janni Niclasen a, b, *, Carsten Obel a, Christian Guldager b, Simone Pleinert b, Jesper Dammeyer b a b

Center for Collaborative Health, Aarhus University, Høegh-Guldbergs Gade 6B, 8000 Aarhus C, Denmark Department of Psychology, University of Copenhagen, Øster Farimagsgade 2A, 1353 Copenhagen K, Denmark

a r t i c l e i n f o

a b s t r a c t

Article history: Received 2 July 2016 Received in revised form 3 September 2016 Accepted 3 September 2016 Available online 5 September 2016

Objective: Negative associations between hearing loss (HL) and behavioural and academic difficulties have been reported. However, most studies are based on small clinical samples. The aim of the present study was to investigate such associations using data from a large-scale non-clinical Danish birth cohort controlling for a large number of relevant confounding factors. Methods: The study applied data from the Aarhus Birth Cohort's 10-12-year-old follow-up (N ¼ 7599). Associations between parent-reported HL on the one hand, and parent- and teacher-reported behavioural difficulties measured by the Strengths and Difficulties Questionnaire (SDQ) and parent-reported academic difficulties on the other hand, were investigated. Results: After controlling for relevant confounding factors, significant associations were observed between parent-reported HL and parent- and teacher-reported Externalising scores, and academic difficulties. Conclusions: Childhood HL is associated with behavioural and academic difficulties. Parent reported HL in a non-clinical cohort is indicative for academic and behavioural difficulties. © 2016 Elsevier Ireland Ltd. All rights reserved.

Keywords: Hearing loss Hearing impairment Behavioural development Academic difficulties Children Cohort SDQ Strengths and difficulties questionnaire Aarhus birth cohort Cohort Non-clinical Parent Parent-report

1. Introduction The prevalence rate of severe to profound congenital or early onset hearing loss (HL) has been estimated to be between one and three per 1000 [14,54,55]. Including milder HL, 14.9% of US children have been found to have low-frequency or high-frequency hearing loss of at least 16-dB hearing level in one or both ears [33]. The ability to hear affects the development of communication and behavioural skills and in turn influences educational outcome and social development. Research has shown, that children with HL is at higher risk for a number of academic, social and behavioural difficulties [19,24]. Childhood HL has also been associated with an increased risk of

* Corresponding author. Center for Collaborative Health Aarhus University Høegh-Guldbergs Gade 6B 8000 Aarhus C Denmark. E-mail address: [email protected] (J. Niclasen). http://dx.doi.org/10.1016/j.ijporl.2016.09.002 0165-5876/© 2016 Elsevier Ireland Ltd. All rights reserved.

mental health problems and behavioural difficulties, with prevalence estimated at between 20 and 40% [7e9]. These include a wide range of mental health problems from milder emotional and behavioural difficulties to pervasive developmental disorders [4,50]. A recent meta-analysis concluded that children and adolescents with HL have emotional and behavioural difficulties, measured by the Strength and Difficulty Questionnaire (SDQ) [13], of a quarter to a third of a standard deviation higher than children without HL [46]. It has finally been shown, that many children with HL face a higher risk of academic difficulties and outcomes in primary and secondary school [19,20,39,51,53]. This is reflected in lower achievement scores [40] as well as lower levels of educational attainment [2,18,21,41,45]. Even a mild HL has been found to negatively impact levels of educational attainment [3,11,18,26,48]. Similarly, studies have also reported that a mild, temporary HL, due to otitis media in early childhood, might lead to academic and

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behavioural difficulties later in school [30,37,44,49]. Overall, two explanations have been provided to delineate the associations between early childhood HL and later academic and behavioural difficulties [7]. The first is a biomedical explanation, which focus on medical and genetic factor associated with both HL and comorbidities of learning and behaviour difficulties. Thus, additional disabilities should be taken into consideration, when investigating associations between HL and developmental outcomes [5,9,50]. The second explanation is multifactorial and involves the indirect effect of psychological and social factors. Focus has by and large been on the escalated impact of childhood language delay. Early childhood hearing impairment increases the risk of delayed language development which in turn affect reading and writing skills [6,25]; and behaviour problems [5,47]. For instance [6], reported a delay in the development of literacy skills of deaf students. This delay could not in itself be explained by the deaf students degree HL, but was to a larger extent associated with their level of language abilities, irrespective of it being oral or signlanguage. Those with fair to good spoken or sign language skills were much less likely to experience literacy delays compared to those with a poor language skills. Thus, it seems as it is not only the direct effect of the hearing impairment per see, but also the indirect mediating effect of language development that can explain the social and cognitive developmental outcomes [24]. The literature has generally shown an association between HL and behavioural and learning development in clinical samples using data from deaf schools or paediatric hospitals. However, studies based on data from large and non-clinical cohorts controlling for relevant covariates are sparse. The aim of the present study was therefore to investigate associations between self-reported childhood HL and academic and behavioural difficulties controlling for relevant confounding factors in a large-scale Danish birth cohort. 2. Methods 2.1. Participants Data for the study were derived from the ongoing Aarhus Birth Cohort (ABC) established in 1989. In 2001, when a sub-sample of the children were between nine and 11 years old, parents of a total of 8244 children were asked to complete a questionnaire concerning the child's health, development, behavioural and academic difficulties [34]. A year later, in 2002, the parents were sent a package of questionnaires including the parent and teacher versions of the Strengths and Difficulties Questionnaire (SDQ) [13]. The parents were asked to pass on the teacher version of the SDQ to their child's primary school teacher. Of the 8244 children in the sample, a total of 7599 provided information about HL. The SDQ was completed by a total of 6642 (88% response rate) parents and 5567 (86% response rate) teachers. 2.2. Measures 2.2.1. Information about the child and the family The questionnaire included information on the child's behaviour and cognitive functioning, physical health, retrospective information about the first six years of the child's life as well as parental history of attention and school problems, lifestyle and physical health [34]. These pieces of information were provided by one of the parents. 2.2.2. Exposure: parent-reported hearing loss The primary exposure was information on self-reported hearing impairment. The parents were asked “Does the child have a hearing

loss”? The question could be answered “Yes” or “No“. Of the total sample of 7599 who responded to this item, a total of 311 (4.1%) agreed to this, whereas 7288 (95.9%) responded “no”. A total of 88 were excluded due missing value. 2.2.3. Outcome: the strengths and difficulties questionnaire (SDQ) The SDQ contains 25 questions asking about different positive and negative aspects of the child's behaviour. It can be rated ‘not true’, ‘somewhat true’ and ‘certainly true’. The questions have been selected on the basis of contemporary nosological concepts as well as factor analytically derived dimensions [12,13,31,32]. Parallel versions of the SDQ have been developed for parents, teachers and young persons. The Danish parent and teacher versions were translated in 2001, implementing standard translation, backtranslation procedures [35,36]. The items load into five scales (Hyperactivity, Emotional, Conduct, Peer problem and Prosocial) each with five items. The five SDQ scales can be used either as five individual scale scores, or in a broader model combining the Peer problem and Emotional problem scales into an Internalising scale, and the Hyperactivity and Conduct scales into an Externalising scale. The factor structure of these two models have been found to be superior in a large-scale Danish study [31]. SDQ scores from parents and teachers were used as outcome measures in the present study. We used the four problem scales (Hyperactivity/inattention, Conduct, Emotional problems, and Peer problems) as dichotomised variables applying the following nationally-developed cut-offs for parent ratings: Hyperactivity/ inattention: 6; Conduct: 3; Emotional problems: 5; and Peer problems: 4. For teachers, the following cut-offs were applied: Hyperactivity/inattention: 7; Conduct: 3; Emotional problems: 5; and Peer problems: 5 [28]. Further, we applied the two broader Internalising/Externalising scales as continuous scores. Goodman [13] suggested that missing data on the SDQ scales are only imputed if a minimum of three (out of five) answers are available on a single scale. It was therefore decided to include cases with a maximum of two missing on a given scale. Missing data was computed based on the average scale score of each participant. 2.2.4. Outcome: academic difficulties Academic difficulties were defined by use of three questions. The first and the second questions concerned reading and spelling abilities, respectively: “Does your child find it difficult to read?” and “Does your child find it difficult to spell?”. The questions could be answered: 1: “No”; 2. “yes, a little”; 3. “Yes, somewhat”; 4. “Yes, a lot”; 5: “don't know”. The third question was: “Has the child received special educational support”? This question could be answered: 1. “No, never”; 2. “Yes, previously”; 3. “Yes, now”. It was decided to dichotomise this outcome into Yes/no. 2.2.5. Confounding factors The following covariates were controlled for in the statistical analyses: parental education, maternal and paternal academic difficulties at school, parental smoking, breastfeeding and age at which the child started walking. On the basis of information on maternal and paternal educational level, a variable on highest household educational level was composed. Four categories were adapted: 1. “No education”(i.e. only primary and lower secondary school) (n ¼ 321); 2. “Yes, short/1e2 years” (n ¼ 936); 3. “Yes, medium length/3e4 years” (n ¼ 3783); 4. “Yes, long/more than four years” (n ¼ 2415). It was decided to control for maternal and paternal academic difficulties at school separately. Academic difficulties at school was composed of two variables, one on difficulties with reading and another on difficulties with spelling. The variables were recoded into three categories, respectively: 1: “no problems” (n ¼ 5796 and 4980, respectively); 2: “some problems” (n ¼ 1461


and 1590, respectively); and 3. “severe problems” (n ¼ 283 and 453, respectively). The maternal and paternal post-natal smoking variables were dichotomies (“yes”/“no”) after which they were composed and recoded into three categories: 1: “yes, two smoking parents” (n ¼ 1962); 2: “yes, one smoking parent” (n ¼ 2689); 3: “no smoking parents” (n ¼ 2941). The breast feeding variable was categorised into four categories according to the length of time the child was breast fed: “No, not breast feeding at all” (n ¼ 344); 1: “yes, 0e6 months” (n ¼ 3194); “yes, 7e12 months” (n ¼ 2974); 4: “yes, >12 months” (n ¼ 1087). The variable measuring the age at which the child started walking was categorised into three categories: 1: “0e11 months” (n ¼ 2299); 2: “12e15 months” (n ¼ 4800) and 3: “>15 months” (n ¼ 500). 2.3. Statistical analysis The overall aim was to investigate possible associations between parent-reported HL on the one hand and behavioural and academic difficulties on the other hand. Firstly, it was decided to describe children with and without HL on a range of background characteristics. One-way ANOVA and Chi Square testing were used to investigate mean differences on background characteristics between children with and without HL [10]. These descriptive statistics were carried out in SPSS version 21. Secondly, behavioural difficulties were analysed by multivariate linear regressions to model HL and associations with SDQ Externalising and Internalising scores controlling for relevant confounders. Further, the four dichotomised problem-SDQ scales (Hyperactivity, Conduct, Emotional, and Peer problems) were assessed using logistic regression models with the given cut-offs identifying the 10% of the sample with the highest problem score. Academic difficulties were analysed by treating spelling and reading difficulties on a categorical level (three categories) and running proportional odds regressions to model these outcomes controlling for relevant confounders. Similarly, use of special education support service was treated as a binary outcome variable and modelled by means of logistic regression. The regression models were all carried out in SAS version 9.4. One set of sensitivity analyses were carried out. In order to investigate the influence of additional disabilities all analysis were rerun excluding children with parent reported additional disabilities. There is no institutional review board at the Department at which the study took place. However, the data was approved by the regional ethic committee - De Videnskabsetiske Komiteer for Region Midtjylland. The parents and teachers were, in writing, made aware that the data collected for research purposes only and verbally gave their consent for the data being used for such studies. The regional ethics committee approved the use of such verbal informed consent procedure. The parent consent was required before any approach was made to the child's teacher. 3. Results 3.1. Descriptive statistics Table 1 shows the background characteristics of the exposure groups, i.e. children with and without HL. Of the children in the cohort parents reported that 4.1% had hearing loss. It appears that the children with HL were reported to be breast-fed in significantly shorter periods of time. Reversely, they were reported to have more periods of hospitalisations, more use of medication, and more episodes of Otitis Media (OM), Tympanostomy tube insertion, and additional disabilities. In the HL group 13.6% reported no episodes

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of OM. Of the 86.4% who have had experiences with OM a total of 79.9% had had Tympanostomy tubes insertion. This is to be compared to 48.3% reporting no episodes of OM in the no-HI group of which 34.8% had had Tympanostomy tubes insertion. For the school-related factors significant differences between the two groups were observed on all included variables, i.e. speech development, difficulties with reading, spelling, mathematics, concentration and bullying. From the adjusted linear regression models in Table 2 it appears that there was a significant association between parent-reported HL and parent- and teacher-reported Externalising scores on the SDQ. Further, parental-rated Internalising scores were approaching significance. Table 3 shows OR for the association between parent-reported HL and dichotomised SDQ outcomes. Of the eight outcomes, five were found to be significant in the expected direction. Two of the remaining three outcomes were approaching significance. Table 4 shows Odds Ratios (OR) between parent-reported hearing problems on the one hand and use of special education support, reading and spelling difficulties, respectively, on the other. Significant differences were persistently found across all three outcomes. 3.2. Sensitivity analyses In order to test the stability of the results, all analyses were rerun excluding children with an additional disability from the analyses. These results proved to be virtually identical to the results of the main analyses (please see online Appendix 1, Tables 5e7). 4. Discussion Previous studies using audiological testing among children aged 6e19 have reported a prevalence of 4.9% of a minimum of 16-dB (high and low frequencies) HL in one or both ears. Based on the better ear, between 1.3% and 2.8% of all children had hearing loss of at least 16-dB HL at individual frequencies of 0.5, 1, 2, 3, and 4 kHz. Based on the worse ear, 5.5%e10.6% of all children had hearing loss at 0.5, 1, 2, 3, and 4 kHz [33]. Based on these figures the parentreported prevalence of HL in the present study reported at 4.1%, indicated that the information on self-reported HL in the present study seem reliable. The main finding of the present study indicates associations between parent reported HL and behavioural and academic difficulties in a non-clinical cohort. These associations remained after controlling for a number of confounding factors. This is overall in line with previous findings, primarily based on clinical samples. Children with a clinical HL have been reported to score higher on externalising and internalising scale scores [29], and have higher rates of peer-problems [46]. It is further well documented that many pupils with HL have academic difficulties [20,24]. Research in the United States has shown that the median reading ability of deaf adolescents leaving secondary school is at a fourth grade level and that only 10% of these students develop age-appropriate academic skills [53]. Similar results have been found in other countries [1,16,56]. The present study adds to this overall picture by reporting such association in non-clinical samples of children. OM and Tympanostomy Tube insertions have been reported as potential predictors and moderators, respectively, for HL and later behavioural and academic difficulties [52]. The percentages reporting no episodes of OM in the no-HL and HL exposure groups of the present study were 48.3% and 13.6%, respectively. In other words, around half of the children in the no-HL group reported childhood experiences with OM, whereas this was true for 86.4% of the HL group. Further, of those reporting episodes of OM the

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Table 1 One way ANOVA and Pearson Chi Square testing for differences in means and percentages between the exposure groups. Hearing loss

Full sample

No

Yes

N

7599 Means (SD) 152 (55) 9.5 (8.1) 10.5 (5.2) 3.7 (3.2) 9.4 (6.8) Percentages 51.0% 78.8% 85.7%

7288 (95.9%) Means (SD) 152 (55) 9.5 (8.1) 10.5 (5.2) 3.7 (3.2) 9.4 (6.8) Percentages 50.9% 79.0% 85.7%

311 (4.1%) Means (SD) 152 (59) 10.0 (8.3) 10.2 (5.8) 3.5 (3.2) 9.4 (6.5) Percentages 52.4% 74.9 84.1%

8.7% 3.0% 27.4% 46.0% 14.9%

8.7% 2.9% 27.3% 46.0% 15.0%

7.8% 4.5% 29.4% 45.6% 12.6%

11.4% 1.8% 12.6% 46.3% 27.8% 95.4% 96.7% 48.3% 41.5% 45.9%

11.2% 1.8% 12.7% 46.3% 28.1% 95.6% 96.8% 48.2% 41.6% 45.9%

17.0% 1.7% 10.9% 47.6% 22.8% 92.6% 95.5% 53.0% 41.0% 45.1%

7.4% 27.3%

7.3% 26.9%

9.6% 36.0%

46.9% 31.7% 20.3% 1.1%

48.3% 32.1% 18.5% 1.1%

13.6% 24.3% 60.8% 1.3%

61.9% 37.9% 0.2% 7.7% 90.3% 97.1% 12.9% 4.3% 7.2% 7.9%

65.0% 34.8% 0.2% 7.5% 90.4% 97.1% 12.4% 3.9% 7.1% 7.9%

20.1% 79.9% 0% 12.5% 88.7% 97.4% 26.6% 14.5% 9.8% 8.0%

11.1% 58.7% 29.7% 0.5% 10.8%

10.4% 59.0% 30.0% 0.5% 10.2%

26.1% 52.1% 21.2% 0.7% 24.2%

74.9% 29.8% 5.1% 0.1%

75.4% 19.5% 4.9% 0.2%

62.8% 27.2% 10.0% 0%

69.5% 25.5% 5.1% 0.4%

70.0% 24.9% 4.8% 0.4%

58.6% 19.8% 11.3% 0.3%

79.5% 18.4% 2.0% 0.2%

79.9% 18.0% 1.9% 0.2%

69.6% 26.8% 3.6% 0%

71.8% 24.4% 3.0% 0.8%

72.2% 24.2% 2.8% 0.9%

61.4% 28.9% 9.4% 0.3%

Housing (M2) After-school care (Hours/week) Television (hours/week) Reading (hours/week) Physical activities (hours/week) Gender (boys) Married (yes)g Rater (M) Education (M)d No Student Yes, 1e2 years Yes, 3e4 years Yes, >4 years Education (P)e No Student Yes, 1e2 years Yes, 3e4 years Yes, >4 years Breast feeding (yes) MRR vaccinej Eat healthy (yes)c Smoking (yes) (M)d,f Smoking (yes) (P)e,f Hospitalisation (yes) Infection Others Otitis Media No Yes, 1e3 episodes Yes, 4 þ episodes Don't know Tympanostomy tubesh No Yes Don't know Medicationb (yes) Day care, 0e3 years (yes) Day care, 3e6 years (yes) Worry about child development (yes)c Additional disabilities (yes) Glasses (yes) Enuresis (yes) Speech developmenta,i: Later than peers Like peers Earlier than peers Don't know Speech therapist (yes) Difficulties reading No Yes, some Yes, a lot Don't know Difficulties spelling No Yes, some Yes, a lot Don't know Difficulties math No Yes, some Yes, a lot Don't know Concentration problems No Yes, some Yes, a lot Don't know Bullying (of others)

P-value

0.85 0.31 0.32 0.26 0.89 0.60 0.09 0.59 0.33

0.018*

0.013* 0.20 0.26 0.84 0.78 0.000***

0.000***

0.000***

0.001** 0.34 0.74 0.000*** 0.000*** 0.08 0.91 0.000***

0.000*** 0.000***

0.000***

0.000***

0.000***

0.001**


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Table 1 (continued ) Hearing loss

Full sample

No

Yes

No Yes, some Yes, a lot Don't know Bullying (by others) No Yes, some Yes, a lot Don't know Special education (yes)

81.7% 11.1% 0.1% 7.1%

81.8% 11.1% 0.1% 7.0%

79.2% 11.1% 0.3% 9.4%

78.4% 18.8% 0.9% 1.9% 17.2%

78.7% 18.6% 0.8% 1.8% 16.6%

72.1% 23.3% 1.3% 3.2% 30.2%

P-value

0.003**

0.000***

*: P < 0.05; **: P < 0.01; ***: P < 0.001. a Married or living together. b Difficulties getting the child to eat healthily. c Smoking after the birth of the child. d M ¼ maternal. e P ¼ paternal. f Of those reporting episodes of Otitis Media (N ¼ 3975). g Medication: periods of at least three month with weekly medication. h Has the rater been worried about child development in the first six years of life?. j MMR vaccine e measles, mumps, and rubella immunisation. i Percentage of parents reporting on speech development.

Table 2 Relative change in mean between parent-reported problems and continuous SDQ Externalising and Internalising scores at age 10e12 years. Models adjusted for the following covariates: household education, maternal school problems, paternal school problems, combined maternal and paternal smoking, breastfeeding and age at which the child was walking. Exposure categories Hearing No Yes Hearing No Yes Hearing No Yes Hearing No Yes

Unadjusted

impairment and parental SDQ externalising scores REF 1.28 impairment and parental SDQ internalising scores REF 1.12 impairment and teacher SDQ externalising scores REF 1.17 impairment and teacher SDQ internalising scores REF 1.04

Adjusted

Table 3 Adjusted Odds Ratios (OR) for the above cut-off Hyperactivity, Conduct, Emotional and Peer-problem scores. Chi Square for the unadjusted models and the Chi square of the likelihood ratio test for the adjusted model are presented. Models adjusted for the following covariates: household education, maternal school problems, paternal school problems, combined maternal and paternal smoking, breastfeeding and age at which the child was walking. Exposure categories

REF 1.24 (1.12e1.38) REF 1.10 (0.99e1.23) REF 1.16 (1.00e1.33) REF 1.00 (0.86e1.15)

percentages reporting Tympanostomy Tubes insertion were 34.8% and 79.9% in the no-HL and HL exposure groups, respectively. Thus, OM seems to be a strong predictor of parent reported HL. Further, Tympanostomy tubes insertion also seem to be an indicator of parent reported HL. This finding is in accordance with previous research [30,37,44,49]. However, other studies have not been able to report such associations between early experiences with OM and later behavioural and academic difficulties [38,42,43]. Still more research is needed to explain the specific developmental pathways between HL, OM/Tympanostomy tubes and behavioural and academic difficulties. Apart from OM, additional disabilities have been reported in the literature to influence the association between HL and behavioural and academic difficulties [5,9,14]. In order to test the influence of additional disabilities one set of sensitivity analyses was carried out. A significant difference in parent-reported additional disability between the children with and without HL was observed in the present study. However, the results remained virtually identical after rerunning the analysis excluding children with additional disabilities from the analyses. One explanation for this finding could be that there were not enough children with additional disabilities in the cohort and thus not enough power to reveal a potential effect of this factor. The level of self-reported additional

Unadjusted

Adjusted

Hearing impairment and parent SDQ hyperactivity scores Chi square 43.23 (1), P < 0.0001 32.43 (1), P < 0.0001 No REF REF Yes 2.95 2.86 (1.99e4.11) Hearing impairment and parent SDQ conduct scores Chi square 3.43 (1), P ¼ 0.06, NS 2.64 (1), P ¼ 0.10, NS No REF REF Yes 1.41 1.40 (0.93e2.08) Hearing impairment and parent SDQ emotional problem scores Chi square 13.92 (1), P < 0.001 11.08 (1), P < 0.001 No REF REF Yes 1.91 1.89 (1.30e2.74) Hearing impairment and parent SDQ peer problem scores Chi square 8.07 (1), P < 0.01 6.31 (1), P < 0.05 No REF REF Yes 1.71 1.69 (1.21e2.53) Hearing impairment and teacher SDQ hyperactivity scores Chi square 10.81 (1), P < 0.001 7.68 (1), P < 0.01 No REF REF Yes 1.90 1.84 (1.20e2.82) Hearing problems and teacher SDQ conduct scores Chi square 8.44 (1), P < 0.01 9.00 (1), P < 0.01 No REF REF Yes 1.71 1.82 (1.23e2.70) Hearing problems and teacher SDQ emotional problem scores Chi square 0.19 (1), P ¼ 0.66, NS 0.00 (1), P ¼ 0.98, NS No REF REF Yes 1.11 1.01 (0.59e1.71) Hearing problems and teacher SDQ peer problem scores Chi square 2.88 (1), P ¼ 0.09, NS 1.94 (1), P ¼ 0.16, NS No REF REF Yes 1.38 1.33 (0.89e1.98)

disabilities among children with HL in the present study was a little lower (14.8%) compared to other studies which have reported levels of additional disabilities to be between 20 and 40% [7,8]. Thus, a potential (small) effect would not be detected in the statistical analyses. A second explanation might be that the parent-reported

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Table 4 Adjusted Odds Ratios (OR) for reading and spelling difficulties and the use of special education support. Chi Square for the unadjusted models and the Chi square of the likelihood ratio test for the adjusted model are presented. Models adjusted for the following covariates: household education, maternal academic difficulties at school, paternal academic difficulties at school, combined maternal and paternal smoking, breastfeeding and age at which the child was walking. Exposure categories

Unadjusted

Hearing impairment and use of special education support Chi square 36.61 (1), P < 0.0001 No REF Yes 2.17 Hearing impairment and reading problems Chi square 27.69 (1), P < 0.0001 No REF Yes 1.86 Hearing impairment and spelling problems Chi square 23.92 (1), P < 0.0001 No REF Yes 1.76

Adjusted 23.11 (1), P < 0.0001 REF 2.01 (1.51e2.68) 18.34 (1), P < 0.0001 REF 1.76 (1.36e2.29) 16.23 (1), P < 0.0001 REF 1.68 (1.31e2.16)

additional disabilities in the present study might include a wide range of problems that may not all be associated with the outcomes. If this is the case then a potential effect of additional disability would be deflated. The specific self-reported disabilities remain unknown in the present studies. Associations between HL and later behavioural problems have previously been investigated from multifactorial and biomedical perspectives. From a multifactorial perspective there has been a focus on psychological and social factors. Some researchers have emphasised language delays as the main explanation for the increased level of behavioural problems among children with HL [5,47]. The two studies have showed that behavioural problems decrease to the same level as for children without HL if their language abilities are good. Spoken language delay, in terms of both production and comprehension, has also been reported as an explanation for later academic difficulties [20,24]. On the basis of the data from the present study it is not possible to evaluate the specific developmental impact of language development. However, it was observed that speech development was more delayed and speech therapy more often used in the HL group compared to the group of children without HL. This might indicate that speech development does play a role in the association between HL and behavioural and academic difficulties in non-clinical samples. 4.1. Strengths and limitations Over the last two decades neonatal hearing screening and new hearing aid technologies have been introduced as standard treatment for children with HL in many western countries [27]. Introduction of paediatric cochlear implantation for children with severe to profound hearing impairment represents one of these changes. It is well documented that these new technologies improve the hearing impaired child's success in oral language development. Further, several studies have also shown that the new technologies have a positive impact on the academic and behavioural development [17,22,23]. However, to which degree the new and improved hearing aid technologies improve behaviour and academic outcome for children with HL is debated. Qi & Mitchel [40] prospectively examined academic outcomes of children with HL and found that, despite technological achievements, children with HL still experience difficulties. With respect to behavioural difficulties, children with CI seems to experience difficulties somewhere below deaf children without CI but above children without HL [17]. Data for the present study was collected in 2002 on children born between 1990 and 1992. Therefore, we were not able to evaluate the

effect of these improvements for children with HL over time. It is on this basis recommend that future studies compare non-clinical cohorts from different points in time. No clinical diagnoses were available in the present study and solely relied on parent reported information. This might have both advantages and disadvantages. It is an obvious limitation of the present study that the parent-reported HL could not be validated by audiological testing. Further, no information was obtained concerning the onset of the HL and therefore not introduced into the analyses. Finally, no information was available about whether the HL was stable, fluctuating or temporary. Future studies should if possible include information on dB hearing loss, onset of the hearing loss and type of hearing loss (conductive or congenital). Unfortunately, the present study included none of these information. Although these factors might add to the picture, previous studies have also found that the degree of HL is not predictive for life outcomes for children with hearing loss [4]. Thus, we do not find the missing of these factors critical. However, the inclusion of parent-reported HL also hold some advantages. The aim of the study was specifically to evaluate associations between parent-reported HL and behavioural and academic difficulties. The parent-reported prevalence of HI in this study was within the prevalence range reported in studies using audiological testing [33], and thus considered valid. Irrespective of medically validated HL, parent-reported HL seems to be a useful indicator of behavioural and academic difficulties. On this basis it is strongly recommended that future studies include both parents reports, that inquire about the impact of HL of the child's daily living, but also objective measures that gives an idea of the actual degree of the hearing loss. Another limitation of the study was that information on HL and behavioural and academic difficulties was rated at the same point in time and thus of cross-sectional nature. It may be that those parents with children with learning and/or behavioural difficulties are more likely to rate their children as having a HL compared to those parents with children without learning and/or behavioural difficulties. Knowledge of the developmental pathways of children with HL remains unknown and longitudinal large-scale, prospective cohort studies are recommended. On the other hand, and obvious strength of the present study was the inclusion of a large-scale non-clinical cohort. Most of the existing studies are based on small clinical samples from deaf schools or paediatric hospitals. Because of the size of the present sample it was possible to control for relevant confounding factors in the statistical analyses. 5. Conclusion Parent-reported hearing loss was found to be associated with child behavioural and academic difficulties. The associations remained after controlling for a number of confounding factors includeing additional disabilities. The study underlines, in accordance with existing studies, that parent-reported childhood HL is to be taken seriously in order to prevent negative developmental outcomes on part of the child. Funding No funding was secured for this study. Acknowledgements None.


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