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Hearing aid use in Finnish children—impact of hearing loss variables and detection delay
International Journal of Pediatric Otorhinolaryngology (2006) 70, 475—480
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Hearing aid use in Finnish children–—impact of hearing loss variables and detection delay Timo I. Marttila *, Jukka O. Karikoski 1 Audiological Department, Ear-, Nose and Throat Clinic, Helsinki University Central Hospital, Haartmaninkatu 4 E, FIN-00029 HUS 29, Helsinki, Finland Received 23 January 2004; received in revised form 12 July 2005; accepted 28 July 2005
KEYWORDS Audiometrical configuration; Binaural; Children; Hearing aid use; Hearing impairment
Summary Objective: The aim was to study the factors contributing to the mode of hearing aid use in children, with special emphasis on hearing loss variables and detection delay. Methods: The subjects were 328 children and adolescents (58.5% boys, 41.5% girls) aged 1—18 years with hearing loss of 30 dB HL in the better ear fitted with hearing aid(s). The study was cross-sectional analysing the mode of using the aid binaurally/ unilaterally or not at all. Results: The children with hearing-impairment ranging from 50 to 90 dB HL used more regularly their hearing aids. In the subjects with hearing loss 80 dB HL the presence of measurable hearing threshold at 4 kHz related significantly to the acceptance of amplification ( p = 0.027). In 19% of the subjects hearing aid was discarded. Bilateral amplification was used in 38%. Unilateral use was the prevailing mode (44%). The younger the children ( p = 0.000) and the worse their hearing loss ( p = 0.008), the more regular their bilateral use was. Early detection of hearing loss and early hearing aid fitting promoted binaural hearing aid use ( p = 0.004). A marked asymmetry in pure tone thresholds was a significant audiological reason for fixed unilateral hearing device use (38%, p = 0.001). Conclusions: The study shows that early detection of hearing loss and early habilitation of hearing increase bilateral use of hearing device and decrease the number of nonusers. Furthermore, residual unaided hearing at 4 kHz significantly improves the use of device. # 2005 Elsevier Ireland Ltd. All rights reserved.
1. Introduction * Corresponding author. Tel.: +358 9 47173692; fax: +358 9 47175037. E-mail addresses: [email protected] (T.I. Marttila), [email protected] (J.O. Karikoski). 1 Tel.: +358 9 47173693.
Universal newborn hearing screening has been recommended as a tool to reduce the well-known delay in identifying childhood-onset hearing impairment [1—5]. This can be accomplished by a
0165-5876/$ — see front matter # 2005 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijporl.2005.07.028
476
screening based on evoked otoacoustic emissions [6—9] and/or by an automated auditory brain stem response measurement [7,9,10]. Universally the goal has been set to detect significant hearingimpairments before the age of 6 months [11]. New York and Colorado have succeeded in decreasing the median delay to 3 months [12]. However, it is difficult to indisputably show the benefit of early intervention to the final outcome, i.e. the acquisition of aural-verbal communication. In this respect the degree of hearing loss severity is not an adequate tool [13,14]. By a timely and optimal amplification with preferably bilateral hearing aids in proper use we tried to alleviate the adverse effects of hearing-impairment on the acquisition of speech and language, academic achievement as well as social on and emotional development. In evaluating the effectiveness of rehabilitative interventions, we need qualitative data on: the children’s acceptance to use their individual hearing device(s); which of them prefer using their aid(s) binaurally/unilaterally or not at all; the impact of hearing loss variables (the severity and asymmetry of hearing loss or the contour of audiogram) and the detection delay on the regular device use, particularly in profoundly deaf children. The study was designed to elucidate these factors basing on a cross-sectional survey of children fitted with hearing aid(s) in southern Finland.
2. Material and methods 2.1. Subjects The material consisted of 328 children and adolescents (58.5% boys, 41.5% girls) aged 1—18 years. In an age-matched population of 270,726, these presented all the children with hearing loss of 30 dB HL in the better ear, fitted with hearing aid(s) during a 7-year-period in Helsinki University Central Hospital, which is responsible for hearing habilitation and rehabilitation in children in the Health care region of Helsinki and Uusimaa (prevalence = 1.2/ 1000) [15]. Binaural fitting of hearing aid was the goal at the outset of rehabilitation unless excluded by otological (aural malformation, chronic infection) or audiological reasons (substantial asymmetry in hearing or discrimination scores). At their regular visits to the audiological department, the subjects were encouraged to use hearing aid bilaterally.
2.2. Hearing measurement Before hearing threshold measurements, all subjects were examined otoscopically to rule out the
T.I. Marttila, J.O. Karikoski
presence of fluid in the middle-ear-cleft. The hearing acuity of the children below the age of 3 years was examined with behavioural orientation audiometry and/or brainstem response measurement presented in detail earlier [2]. Those aged 3—6 years gave their responses as in play audiometry. Older subjects responded in a conventional manner. The air-conducted thresholds were examined in a sound proof booth at 0.25—8 kHz with Madsen OB-70 or OB822 diagnostic audiometer calibrated according to the ISO-389 standards (1985), employing TDH-39 headphones.
2.3. Data compilation Data from the most recent and reliable hearing tests were used. In 292 cases, a pure-tone audiogram was available and their pure-tone average and hearing aid use were related. PTA (pure-tone average at the frequencies of 0.5, 1 and 2 kHz in the better ear; right ear if equal hearing) defined their hearing threshold. Although not included in the PTA, the 4 kHz thresholds were registered. In 36 children a formal pure-tone audiogram was not accomplished, but their hearing loss in the better ear was estimated to be 30 dB HL based on a behavioural observation sound field test (24/36) or brainstem response measurement (12/36). These children were included in the data to relate their hearing aid use to gender and to their ages at data acquisition (n = 328). The contour of audiogram was defined as downward sloping when the threshold deteriorated more than 20 dB from 0.5 to 2.0 kHz. A PTA difference of 15 dB or more indicated an asymmetry. When no threshold was obtained on the maximal output level of the audiometer the numerical value of 130 dB HL was given to the frequency as suggested by the British Society of Audiology [16]. The hearing impairment was defined as mild (26—40 dB HL), moderate (41— 60 dB HL), severe (61—80 dB HL) and profound (>81 dB HL) [17]. The use of hearing aid was ascertained from the hospital records, the reports of rehabilitation instructors (making house calls, visiting kindergartens and schools) and the regular reports by speech therapists. Detailed information was also obtained at the meetings of the staff of the audiological department and from the personnel of the special schools and kindergartens for the deaf and the hardof-hearing. Children fitted with hearing aid(s) visited the audiological department at least once a year for audiometry and hearing aid maintenance. The use of hearing aid was assessed as bilateral, right- or left-sided unilateral, alternating unilateral or discarded.
Hearing aid use in Finnish children
477
2.4. Statistical analysis The data were analysed with the Systat Statistical Software for Windows, version 5.2, IL, USA. The fourfold and larger contingency tables were tested by chi-analysis. Fisher’s exact probability test for four-fold tables was employed when the frequencies were low. The multiple linear regression model was used in evaluating linearity between the dependent and the independent variables. The dependent variable was hearing aid use. The pure tone average of the better hearing ear, the age at hearing aid fitting and the age at data acquisition served as independent variables. The correlation coefficients between the dependent and the independent variables were evaluated with a post hoc test to examine whether they differed significantly from zero.
3. Results
Fig. 1 Ages of 328 children at data acquisition related to hearing aid use (histogram of binaural, unilateral use and nonusers).
Table 1 depicts the use of hearing aids in 192 (58.5%) boys and 136 (41.5%) girls. Among the girls (17.6%) the proportion of nonusers was smaller than among the boys (19.4%). Hearing aid was not employed in 18.6% of all the subjects. For bilateral amplification the percentage was as high as 37.8%. Using hearing aid unilaterally was the prevailing mode (43.6%). Gender had no influence on it (chi-square = 0.14, d.f. = 2, p = 0.93). The use of hearing aid at different ages is shown in Fig. 1. Bilateral use was most common in the years preceding school entrance, i.e. at the age of seven. From the age of ten onwards, the averaged proportion of nonusers was 25%. Between genders the hearing acuity did not differ significantly (arithmetic mean and standard error of mean, boys 67.8 dB, 2.2 and girls 67.7 dB, 2.5). The detection delay (age at hearing aid fitting) influenced statistically significantly the mode of hearing aid use (r = 0.17, n = 292, F = 8.30, p = 0.004). The earlier the hearing aid was fitted the higher was the percentage of subjects using
their device bilaterally. Also statistically significantly, the younger the children (age at data acquisition) (r = 0.25, n = 292, F = 19.41, p = 0.000) and the worse their hearing loss (r = 0.15, n = 292, F = 7.07, p = 0.008), the more regular their bilateral use aids. Asymmetrical hearing was the most significant variable contributing to the fixed unilateral aid use (37.5%, 42/112; chi-square = 16.09, d.f. = 3, p = 0.001) (Table 2). The children with asymmetrical losses, aided unilaterally, showed no preference between the better and the worse ear (chisquare = 3.87, d.f. = 2, p = 0.144). Neither was there any ear preponderance in symmetrical losses. The children with steeply downwards sloping audiograms were more frequently nonusers (22.2%, 16/ 72) than those with flat audiograms (16.4%, 36/220), but the difference was not statistically significant (Fisher’s test, p = 0.341). Table 3 shows the hearing loss severity in relation to hearing aid use in 292 subjects. In mild (<40 dB
Table 1 Hearing aid use in children and alodescents with 30 dB hearing loss in the better ear Mode of hearing aid use
Boys n
Bilateral Alternating unilaterally Unilateral, right ear Unilateral, left ear Not in use Total
Girls %
n
Total %
n
%
72 17 33 33 37
37.5 8.7 17.2 17.2 19.4
52 8 23 29 24
38.2 5.9 16.9 21.4 17.6
124 25 56 62 61
37.8 7.6 17.1 18.9 18.6
192
100.0
136
100.0
328
100.0
The subjects also include the children examined with behavioural audiometry and brain stem response measurement (n = 328).
478
T.I. Marttila, J.O. Karikoski
Table 2 The impact of asymmetry of hearing loss and configuration of audiogram on the mode of hearing aid use in children with PTA 30 dB HL in the better ear (n = 292) Mode of hearing aid use
Asymmetrical hearing n
Sloping audiogram
%
n
Total
%
n
%
Bilateral Alternating unilaterally Unilateral, right ear Unilateral, left ear Not in use
14 2 16 26 7
21.5 3.1 24.6 40.0 10.8
28 4 8 16 16
38.9 5.6 11.1 22.2 22.2
110 18 52 60 52
37.7 6.2 17.8 20.5 17.8
Total
65
100.0
72
100.0
292
100.0
HL) and equal or over 90 dB HL losses the proportion of nonusers was similar, (36.6%, 22/60) and (38.4%, 33/86). We analysed the hearing losses of 80 dB HL (n = 88) more thoroughly. These cases were dichotomised to users and nonusers, in which gender did not influence the use of hearing aid (Fisher’s test, p = 0.184). Measurable hearing at 4 kHz in severe (88.9%, 32/36) and in profound (41.8%, 28/67) losses was related statistically almost significantly to the acceptance of amplification (Fisher’s test, p = 0.027).
more severe losses of their peers [2]. This explains partially the increasing percentage of the nonusers older than 10 years. Gradually adolescents begin to make use of amplification again and the number of nonusers is at the level of 20% of all those fitted with a hearing aid. In our study we have shown the importance of early intervention in hearing loss. Delayed habilitation or rehabilitation significantly diminishes the percentage of subjects using hearing aid bilaterally. Consequently the nonusers increase. The reasons for discarding the device are audiological and exogenic. The nonusers mimic the behaviour of their peers in schools and begin to communicate solely visually using sign language. In puberty, the children who do not benefit from their hearing aids refuse to use them. Some children prefer unilateral use to a more convenient amplification. In mild hearing losses children can manage without amplification or discard hearing aid because of family habits or opinions. According to a Finnish study, children using mainly manual communication have a hearing-impairment of 90 dB HL or worse. All children with a PTA worse than 120 dB HL use signing only [14]. Parving concluded that the outcome of preschool intervention is related predominantly to the degree of hearing loss [19]. A hearing level of less than 75 dB HL facilitates the attendance at normal school. In
4. Discussion The compliance of hearing aid use during the first years of habilitation reflects the procedure used by the audiological clinic. The main goal is to utilize the hearing acuity as thoroughly as possible. The most important objective of the habilitative procedures is speech acquisition. Markides reported the proportion of children not using their aids increasing with age to 28% [18]. The girls made better use of their aids. Our finding that the use of hearing aid diminishes in teenagers agrees with Markides’ results [18]. In both absolute and proportional numbers, the nonusers are most frequent among children with a PTA of 30—39 dB HL. Overall, their hearing-impairments are detected later than the
Table 3 Relation of hearing loss severity to hearing aid use in 292 children (binaural, unilateral and nonusers) Mode of hearing aid use
Pure tone average (0.5, 1 and 2 kHz) (dB HL) 30 n
Bilateral 7 Unilateral 31 Not in use 22 Total
40 %
n
11.7 11 51.7 29 36.6 6
50 %
n
23.9 12 63.0 19 13.1 0
60 %
n
38.7 20 61.3 12 0.0 0
70 %
n
62.5 11 37.5 9 0.0 0
80 %
n
55.0 12 45.0 5 0.0 0
90 % 70.6 29.4 0.0
n 7 8 4
100 %
n
36.8 18 42.1 11 21.1 12
110 % 43.9 26.8 29.3
n 9 6 5
120 %
n %
45.0 3 30.0 0 25.0 3
50.0 0.0 50.0
60 100.0 46 100.0 31 100.0 32 100.0 20 100.0 17 100.0 19 100.0 41 100.0 20 100.0 6 100.0
Hearing aid use in Finnish children
these hearing losses the proper use of hearing aids is important. Vesterager and Parving related hearing aid use to the severity of hearing-impairment in children. The ones with a hearing loss of 60—89 dB HL used their aids more regularly than those with milder or more profound hearing-impairments [13]. In our unselected material, the children with hearing loss between 50 and 90 dB HL used their aids most regularly. This agrees with the figures reported by Vesterager and Parving [13]. In dichotic listening, a right ear advantage for linguistic tasks reflects a left-hemisphere specialization, and a left ear advantage for prosodic tasks reflects a right-hemisphere specialization [20]. The left hemisphere is dominant in all complex linguistic tasks [21,22]. Therefore, the right ear is believed to dominate in children with normal hearing. In our material, no ear preponderance was found in unilaterally aided children with symmetrical losses. Asymmetry in hearing acuity is the most important audiological reason for fixed unilateral use of hearing aid. The data presented show that even in the most profound hearing losses the nonusers never outnumber those who make at least some use of their devices. The analysis of the children with a hearing loss of 80 dB HL revealed the importance of residual hearing at 4 kHz. The Finnish language is considerably redundant having phonologic categories that make the language easy to discriminate, which can modify favourably the impact of hearing loss severity on the acquisition of aural versus verbal communication [14,23—25]. To conclude, the study emphasizes the importance of early detection of hearing loss and early habilitation. Consequently a better compliance to use hearing device bilaterally is anticipated resulting in decreasing number of nonusers. The children with residual unaided hearing at 4 kHz should be encouraged to use their hearing devices at least unilaterally.
References [1] P.K. Kuhl, K.A. Williams, F. Lacerda, K.N. Stevens, B. Lindholm, Linguistic experience alters phonetic perception in infants by six months of age, Science 255 (1992) 606— 608. [2] T.I. Marttila, J.O. Karikoski, Identification of childhood hearing-impairment in Uusimaa County, Finland, Int. J. Pediatr. Otorhinolaryngol. 34 (1996) 45—51. [3] C. Yoshinaga-Itano, A.L. Sedey, D.K. Coulter, Al. Mehl, Language of early- and later-identified children with hearing loss, Pediatrics 102 (1998) 1161—1171. [4] E. Ma ¨ki-Torkko, Childhood hearing-impairments and hearing screening, Thesis, Acta Universitatis Ouluensis, Oulu, 1998.
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[5] The European consensus development conference on neonatal hearing screening (Milan, 1998), Eur. Arch. Otorhinolaryngol 255 (1998) 521—522. [6] A. Parving, G. Salomon, The effect of neonatal universal hearing screening in a health surveillance perspective — a controlled study of two health authority districts, Audiology 35 (1996) 158—168. [7] K.J. Doyle, B. Burggraaff, S. Fujikawa, J. Kim, Newborn hearing screening by otoacoustic emissions and automated auditory brainstem response, Int. J. Pediatr. Otorhinolaryngol. 41 (1997) 111—119. [8] L.M. Elden, W.P. Potsic, Screening and prevention of hearing loss in children, Curr. Opin. Pediatr. 14 (2002) 723—730. [9] J. Jakubicova, Z. Kabatova, M. Zavodna, Identification of hearing loss in newborns by transient otoacoustic emissions, Int. J. Pediatr. Otorhinolaryngol. 67 (2003) 15—18. [10] P.J. Yoon, M. Price, K. Gallagher, B.E. Fleisher, A.H. Messner, The need for long-term audiologic follow-up of neonatal intensive care unit (NICU) graduates, Int. J. Pediatr. Otorhinolaryngol. 67 (2003) 353—357. [11] Joint Committee on Infant Hearing, Year 2000 position statement: principles and guidelines for early hearing detection and intervention programs, Am. J. Audiol. 9 (2000) 9—29. [12] L. Dalzell, M. Orlando, M. MacDonald, A. Berg, M. Bradley, A. Cacace, et al. The New York State universal newborn hearing screening demonstration project: ages of hearing identification, hearing aid fitting, and enrollment in early intervention, Ear Hear 21 (2000) 118—130. [13] V. Vesterager, A. Parving, Rehabilitation of hearing-impaired children: intervention and outcome, Audiology 34 (1995) 207—217. [14] T. Jauhiainen, J.O. Karikoski, T.I. Marttila, The predominant mode of communication-oral or sign–—as an outcome measure of rehabilitation in hearing impaired children, in: R.J. Ruben, P. Karma (Eds.), Advances in Pediatric Otorhinolaryngology, Proceedings of the Seventh International Congress of Pediatric Otorhinolaryngology, 7—10 June 1998, Elsevier, CD-ROM, Helsinki, Finland. [15] J.O. Karikoski, T.I. Marttila, Prevalence of childhood hearing-impairment in southern Finland, Scand. Audiol. 24 (1995) 237—241. [16] The British Society of Audiology, Descriptors for pure tone audiograms, Br. J. Audiol. 22 (1988) 123. [17] World Health Organization, Grades of hearing-impairment, Network News 1991, no. 1. [18] A. Markides, The use of individual hearing aids by hearingimpaired children: a long-term survey, 1977—1987, Bri. J. Audiol. 23 (1989) 123—132. [19] A. Parving, Intervention and the hearing-impaired child — an evaluation of outcome, Int. J. Pediatr. Otorhinolaryngol. 23 (1992) 151—159. [20] G.M. Grimshaw, K.M. Kwasny, E. Covell, R.A. Johnson, The dynamic nature of language lateralization: effects of lexical and prosodic factors, Neuropsychologia 41 (2003) 1008—1019. [21] P.M. Matthews, J. Adcock, Y. Chen, S. Fu, J.T. Devlin, M.F. Rushworth, et al. Confirmed a role for the left inferior frontal cortex in semantic processing. Towards understanding language organisation in the brain using fMRI, Hum. Brain Mapp. 18 (2003) 239—247. [22] P. Marangolo, C. Incoccia, L. Pizzamiglio, U. Sabatini, A. Castriota-Scanderbeg, C. Burani, The right hemisphere involvement in the processing of morphologically derived words, J. Cogn. Neurosci. 15 (2003) 364—371. [23] L. Hakulinen, Suomen kielen rakenne ja kehitys, Otava, Helsinki, 1941.
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[24] A. Palva, Filtered speech audiometry. Basic studies with Finnish speech towards the creation of a method for the diagnosis of central hearing disorders, Acta Otolaryngol (Stockh) (Suppl.) (1965) 210.
T.I. Marttila, J.O. Karikoski
[25] H.J. Kiukaanniemi, P. Mattila, Long-term speech spectra. A computerized method of measurement and a comparative study of Finnish and English data, Scand. Audiol. 9 (1980) 67—72.
www.elsevier.com/locate/ijporl
Hearing aid use in Finnish children–—impact of hearing loss variables and detection delay Timo I. Marttila *, Jukka O. Karikoski 1 Audiological Department, Ear-, Nose and Throat Clinic, Helsinki University Central Hospital, Haartmaninkatu 4 E, FIN-00029 HUS 29, Helsinki, Finland Received 23 January 2004; received in revised form 12 July 2005; accepted 28 July 2005
KEYWORDS Audiometrical configuration; Binaural; Children; Hearing aid use; Hearing impairment
Summary Objective: The aim was to study the factors contributing to the mode of hearing aid use in children, with special emphasis on hearing loss variables and detection delay. Methods: The subjects were 328 children and adolescents (58.5% boys, 41.5% girls) aged 1—18 years with hearing loss of 30 dB HL in the better ear fitted with hearing aid(s). The study was cross-sectional analysing the mode of using the aid binaurally/ unilaterally or not at all. Results: The children with hearing-impairment ranging from 50 to 90 dB HL used more regularly their hearing aids. In the subjects with hearing loss 80 dB HL the presence of measurable hearing threshold at 4 kHz related significantly to the acceptance of amplification ( p = 0.027). In 19% of the subjects hearing aid was discarded. Bilateral amplification was used in 38%. Unilateral use was the prevailing mode (44%). The younger the children ( p = 0.000) and the worse their hearing loss ( p = 0.008), the more regular their bilateral use was. Early detection of hearing loss and early hearing aid fitting promoted binaural hearing aid use ( p = 0.004). A marked asymmetry in pure tone thresholds was a significant audiological reason for fixed unilateral hearing device use (38%, p = 0.001). Conclusions: The study shows that early detection of hearing loss and early habilitation of hearing increase bilateral use of hearing device and decrease the number of nonusers. Furthermore, residual unaided hearing at 4 kHz significantly improves the use of device. # 2005 Elsevier Ireland Ltd. All rights reserved.
1. Introduction * Corresponding author. Tel.: +358 9 47173692; fax: +358 9 47175037. E-mail addresses: [email protected] (T.I. Marttila), [email protected] (J.O. Karikoski). 1 Tel.: +358 9 47173693.
Universal newborn hearing screening has been recommended as a tool to reduce the well-known delay in identifying childhood-onset hearing impairment [1—5]. This can be accomplished by a
0165-5876/$ — see front matter # 2005 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijporl.2005.07.028
476
screening based on evoked otoacoustic emissions [6—9] and/or by an automated auditory brain stem response measurement [7,9,10]. Universally the goal has been set to detect significant hearingimpairments before the age of 6 months [11]. New York and Colorado have succeeded in decreasing the median delay to 3 months [12]. However, it is difficult to indisputably show the benefit of early intervention to the final outcome, i.e. the acquisition of aural-verbal communication. In this respect the degree of hearing loss severity is not an adequate tool [13,14]. By a timely and optimal amplification with preferably bilateral hearing aids in proper use we tried to alleviate the adverse effects of hearing-impairment on the acquisition of speech and language, academic achievement as well as social on and emotional development. In evaluating the effectiveness of rehabilitative interventions, we need qualitative data on: the children’s acceptance to use their individual hearing device(s); which of them prefer using their aid(s) binaurally/unilaterally or not at all; the impact of hearing loss variables (the severity and asymmetry of hearing loss or the contour of audiogram) and the detection delay on the regular device use, particularly in profoundly deaf children. The study was designed to elucidate these factors basing on a cross-sectional survey of children fitted with hearing aid(s) in southern Finland.
2. Material and methods 2.1. Subjects The material consisted of 328 children and adolescents (58.5% boys, 41.5% girls) aged 1—18 years. In an age-matched population of 270,726, these presented all the children with hearing loss of 30 dB HL in the better ear, fitted with hearing aid(s) during a 7-year-period in Helsinki University Central Hospital, which is responsible for hearing habilitation and rehabilitation in children in the Health care region of Helsinki and Uusimaa (prevalence = 1.2/ 1000) [15]. Binaural fitting of hearing aid was the goal at the outset of rehabilitation unless excluded by otological (aural malformation, chronic infection) or audiological reasons (substantial asymmetry in hearing or discrimination scores). At their regular visits to the audiological department, the subjects were encouraged to use hearing aid bilaterally.
2.2. Hearing measurement Before hearing threshold measurements, all subjects were examined otoscopically to rule out the
T.I. Marttila, J.O. Karikoski
presence of fluid in the middle-ear-cleft. The hearing acuity of the children below the age of 3 years was examined with behavioural orientation audiometry and/or brainstem response measurement presented in detail earlier [2]. Those aged 3—6 years gave their responses as in play audiometry. Older subjects responded in a conventional manner. The air-conducted thresholds were examined in a sound proof booth at 0.25—8 kHz with Madsen OB-70 or OB822 diagnostic audiometer calibrated according to the ISO-389 standards (1985), employing TDH-39 headphones.
2.3. Data compilation Data from the most recent and reliable hearing tests were used. In 292 cases, a pure-tone audiogram was available and their pure-tone average and hearing aid use were related. PTA (pure-tone average at the frequencies of 0.5, 1 and 2 kHz in the better ear; right ear if equal hearing) defined their hearing threshold. Although not included in the PTA, the 4 kHz thresholds were registered. In 36 children a formal pure-tone audiogram was not accomplished, but their hearing loss in the better ear was estimated to be 30 dB HL based on a behavioural observation sound field test (24/36) or brainstem response measurement (12/36). These children were included in the data to relate their hearing aid use to gender and to their ages at data acquisition (n = 328). The contour of audiogram was defined as downward sloping when the threshold deteriorated more than 20 dB from 0.5 to 2.0 kHz. A PTA difference of 15 dB or more indicated an asymmetry. When no threshold was obtained on the maximal output level of the audiometer the numerical value of 130 dB HL was given to the frequency as suggested by the British Society of Audiology [16]. The hearing impairment was defined as mild (26—40 dB HL), moderate (41— 60 dB HL), severe (61—80 dB HL) and profound (>81 dB HL) [17]. The use of hearing aid was ascertained from the hospital records, the reports of rehabilitation instructors (making house calls, visiting kindergartens and schools) and the regular reports by speech therapists. Detailed information was also obtained at the meetings of the staff of the audiological department and from the personnel of the special schools and kindergartens for the deaf and the hardof-hearing. Children fitted with hearing aid(s) visited the audiological department at least once a year for audiometry and hearing aid maintenance. The use of hearing aid was assessed as bilateral, right- or left-sided unilateral, alternating unilateral or discarded.
Hearing aid use in Finnish children
477
2.4. Statistical analysis The data were analysed with the Systat Statistical Software for Windows, version 5.2, IL, USA. The fourfold and larger contingency tables were tested by chi-analysis. Fisher’s exact probability test for four-fold tables was employed when the frequencies were low. The multiple linear regression model was used in evaluating linearity between the dependent and the independent variables. The dependent variable was hearing aid use. The pure tone average of the better hearing ear, the age at hearing aid fitting and the age at data acquisition served as independent variables. The correlation coefficients between the dependent and the independent variables were evaluated with a post hoc test to examine whether they differed significantly from zero.
3. Results
Fig. 1 Ages of 328 children at data acquisition related to hearing aid use (histogram of binaural, unilateral use and nonusers).
Table 1 depicts the use of hearing aids in 192 (58.5%) boys and 136 (41.5%) girls. Among the girls (17.6%) the proportion of nonusers was smaller than among the boys (19.4%). Hearing aid was not employed in 18.6% of all the subjects. For bilateral amplification the percentage was as high as 37.8%. Using hearing aid unilaterally was the prevailing mode (43.6%). Gender had no influence on it (chi-square = 0.14, d.f. = 2, p = 0.93). The use of hearing aid at different ages is shown in Fig. 1. Bilateral use was most common in the years preceding school entrance, i.e. at the age of seven. From the age of ten onwards, the averaged proportion of nonusers was 25%. Between genders the hearing acuity did not differ significantly (arithmetic mean and standard error of mean, boys 67.8 dB, 2.2 and girls 67.7 dB, 2.5). The detection delay (age at hearing aid fitting) influenced statistically significantly the mode of hearing aid use (r = 0.17, n = 292, F = 8.30, p = 0.004). The earlier the hearing aid was fitted the higher was the percentage of subjects using
their device bilaterally. Also statistically significantly, the younger the children (age at data acquisition) (r = 0.25, n = 292, F = 19.41, p = 0.000) and the worse their hearing loss (r = 0.15, n = 292, F = 7.07, p = 0.008), the more regular their bilateral use aids. Asymmetrical hearing was the most significant variable contributing to the fixed unilateral aid use (37.5%, 42/112; chi-square = 16.09, d.f. = 3, p = 0.001) (Table 2). The children with asymmetrical losses, aided unilaterally, showed no preference between the better and the worse ear (chisquare = 3.87, d.f. = 2, p = 0.144). Neither was there any ear preponderance in symmetrical losses. The children with steeply downwards sloping audiograms were more frequently nonusers (22.2%, 16/ 72) than those with flat audiograms (16.4%, 36/220), but the difference was not statistically significant (Fisher’s test, p = 0.341). Table 3 shows the hearing loss severity in relation to hearing aid use in 292 subjects. In mild (<40 dB
Table 1 Hearing aid use in children and alodescents with 30 dB hearing loss in the better ear Mode of hearing aid use
Boys n
Bilateral Alternating unilaterally Unilateral, right ear Unilateral, left ear Not in use Total
Girls %
n
Total %
n
%
72 17 33 33 37
37.5 8.7 17.2 17.2 19.4
52 8 23 29 24
38.2 5.9 16.9 21.4 17.6
124 25 56 62 61
37.8 7.6 17.1 18.9 18.6
192
100.0
136
100.0
328
100.0
The subjects also include the children examined with behavioural audiometry and brain stem response measurement (n = 328).
478
T.I. Marttila, J.O. Karikoski
Table 2 The impact of asymmetry of hearing loss and configuration of audiogram on the mode of hearing aid use in children with PTA 30 dB HL in the better ear (n = 292) Mode of hearing aid use
Asymmetrical hearing n
Sloping audiogram
%
n
Total
%
n
%
Bilateral Alternating unilaterally Unilateral, right ear Unilateral, left ear Not in use
14 2 16 26 7
21.5 3.1 24.6 40.0 10.8
28 4 8 16 16
38.9 5.6 11.1 22.2 22.2
110 18 52 60 52
37.7 6.2 17.8 20.5 17.8
Total
65
100.0
72
100.0
292
100.0
HL) and equal or over 90 dB HL losses the proportion of nonusers was similar, (36.6%, 22/60) and (38.4%, 33/86). We analysed the hearing losses of 80 dB HL (n = 88) more thoroughly. These cases were dichotomised to users and nonusers, in which gender did not influence the use of hearing aid (Fisher’s test, p = 0.184). Measurable hearing at 4 kHz in severe (88.9%, 32/36) and in profound (41.8%, 28/67) losses was related statistically almost significantly to the acceptance of amplification (Fisher’s test, p = 0.027).
more severe losses of their peers [2]. This explains partially the increasing percentage of the nonusers older than 10 years. Gradually adolescents begin to make use of amplification again and the number of nonusers is at the level of 20% of all those fitted with a hearing aid. In our study we have shown the importance of early intervention in hearing loss. Delayed habilitation or rehabilitation significantly diminishes the percentage of subjects using hearing aid bilaterally. Consequently the nonusers increase. The reasons for discarding the device are audiological and exogenic. The nonusers mimic the behaviour of their peers in schools and begin to communicate solely visually using sign language. In puberty, the children who do not benefit from their hearing aids refuse to use them. Some children prefer unilateral use to a more convenient amplification. In mild hearing losses children can manage without amplification or discard hearing aid because of family habits or opinions. According to a Finnish study, children using mainly manual communication have a hearing-impairment of 90 dB HL or worse. All children with a PTA worse than 120 dB HL use signing only [14]. Parving concluded that the outcome of preschool intervention is related predominantly to the degree of hearing loss [19]. A hearing level of less than 75 dB HL facilitates the attendance at normal school. In
4. Discussion The compliance of hearing aid use during the first years of habilitation reflects the procedure used by the audiological clinic. The main goal is to utilize the hearing acuity as thoroughly as possible. The most important objective of the habilitative procedures is speech acquisition. Markides reported the proportion of children not using their aids increasing with age to 28% [18]. The girls made better use of their aids. Our finding that the use of hearing aid diminishes in teenagers agrees with Markides’ results [18]. In both absolute and proportional numbers, the nonusers are most frequent among children with a PTA of 30—39 dB HL. Overall, their hearing-impairments are detected later than the
Table 3 Relation of hearing loss severity to hearing aid use in 292 children (binaural, unilateral and nonusers) Mode of hearing aid use
Pure tone average (0.5, 1 and 2 kHz) (dB HL) 30 n
Bilateral 7 Unilateral 31 Not in use 22 Total
40 %
n
11.7 11 51.7 29 36.6 6
50 %
n
23.9 12 63.0 19 13.1 0
60 %
n
38.7 20 61.3 12 0.0 0
70 %
n
62.5 11 37.5 9 0.0 0
80 %
n
55.0 12 45.0 5 0.0 0
90 % 70.6 29.4 0.0
n 7 8 4
100 %
n
36.8 18 42.1 11 21.1 12
110 % 43.9 26.8 29.3
n 9 6 5
120 %
n %
45.0 3 30.0 0 25.0 3
50.0 0.0 50.0
60 100.0 46 100.0 31 100.0 32 100.0 20 100.0 17 100.0 19 100.0 41 100.0 20 100.0 6 100.0
Hearing aid use in Finnish children
these hearing losses the proper use of hearing aids is important. Vesterager and Parving related hearing aid use to the severity of hearing-impairment in children. The ones with a hearing loss of 60—89 dB HL used their aids more regularly than those with milder or more profound hearing-impairments [13]. In our unselected material, the children with hearing loss between 50 and 90 dB HL used their aids most regularly. This agrees with the figures reported by Vesterager and Parving [13]. In dichotic listening, a right ear advantage for linguistic tasks reflects a left-hemisphere specialization, and a left ear advantage for prosodic tasks reflects a right-hemisphere specialization [20]. The left hemisphere is dominant in all complex linguistic tasks [21,22]. Therefore, the right ear is believed to dominate in children with normal hearing. In our material, no ear preponderance was found in unilaterally aided children with symmetrical losses. Asymmetry in hearing acuity is the most important audiological reason for fixed unilateral use of hearing aid. The data presented show that even in the most profound hearing losses the nonusers never outnumber those who make at least some use of their devices. The analysis of the children with a hearing loss of 80 dB HL revealed the importance of residual hearing at 4 kHz. The Finnish language is considerably redundant having phonologic categories that make the language easy to discriminate, which can modify favourably the impact of hearing loss severity on the acquisition of aural versus verbal communication [14,23—25]. To conclude, the study emphasizes the importance of early detection of hearing loss and early habilitation. Consequently a better compliance to use hearing device bilaterally is anticipated resulting in decreasing number of nonusers. The children with residual unaided hearing at 4 kHz should be encouraged to use their hearing devices at least unilaterally.
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