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Heather M Fortnum a MRC Institute of Hearing
Research, University Park, Nottingham NG7 2RD, b Human Communication and Deafness Group, University of
Manchester, Manchester M13 9PL Correspondence to: Dr Fortnum hf{at}ihr.mrc.ac.uk
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Abstract |
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Objective:
To estimate the prevalence of confirmed
permanent childhood hearing impairment and its profile across age and
degree of impairment in the United Kingdom.
Design:
Retrospective total ascertainment through sources in the health and education sectors by postal questionnaire.
Setting:
Hospital based otology and audiology
departments, community health clinics, education services for hearing
impaired children.
Participants:
Children born from 1980 to 1995, resident in United Kingdom in 1998, with severe permanent childhood
hearing impairment (hearing level in the better ear >40 dB averaged
over 0.5, 1, 2, and 4 kHz).
Main outcome measures:
Numbers of cases with date of
birth and severity of impairment converted to prevalences for each
annual birth cohort (cases/1000 live births) and adjusted for underascertainment.
Results:
26 000 notifications ascertained 17 160
individual children. Prevalence rose from 0.91 (95% confidence
interval 0.85 to 0.98) for 3 year olds to 1.65 (1.62 to 1.68) for
children aged 9-16 years. Adjustment for underascertainment increased
estimates to 1.07 (1.03 to 1.12) and 2.05 (2.02 to 2.08). Comparison
with previous studies showed that prevalence increases with age, rather than declining with year of birth.
Conclusions:
Prevalence of confirmed permanent
childhood hearing impairment increases until the age of 9 years to a
level higher than previously estimated. Relative to current yields of universal neonatal hearing screening in the United Kingdom, which are
close to 1/1000 live births, 50-90% more children are diagnosed with
permanent childhood hearing impairment by the age of 9 years. Paediatric audiology services must have the capacity to achieve early
identification and confirmation of these additional cases.
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What is already known on this topic
What this study adds
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Introduction |
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Permanent childhood hearing impairment can have a devastating impact on communication skills,1 educational attainment,2 and quality of life, 3 4 with a high cost to society.5 Improved outcomes for children with congenital impairment are associated with confirmation and intervention by 6 months of age.6 Yet the median age of confirmation of congenital impairments has exceeded 18 months, even in regions of the United Kingdom and United States with good paediatric audiology services. 7 8 Universal neonatal hearing screening 9 10 has the potential to reduce the age at confirmation of congenital impairments.11 However, not all hearing impairments manifest themselves at birth, and screening programmes must be complemented by services that can confirm and manage cases where impairment first shows itself postnatally. No national register of hearing impaired children exists for the United Kingdom, and accurate estimates of the prevalence of permanent childhood hearing impairment and of its profile across age and degree of impairment are unavailable. We have provided such estimates at a time when paediatric audiology services in the United Kingdom are being transformed by the introduction of universal neonatal hearing screening12 and the modernisation of hearing aid services.13
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Glossary
Congenital impairment Progressive impairment Late onset impairment Acquired impairment Confirmation of hearing impairment Notification Ascertainment Total ascertainment Prevalence of confirmed cases |
Previous studies of the prevalence of permanent childhood hearing
impairment display two limitations.
7 8 14-16
Firstly, they ascertained relatively small samples (under 700 children) and so did not define the relation between prevalence, age, and degree
of impairment precisely. Secondly, they did not estimate the extent of
underascertainment. We examined these issues by estimating prevalence
from a total ascertainment of hearing impaired children in the United
Kingdom (>17 000) and by employing capture-recapture analysis
17 18
to adjust for underascertainment. We
estimated the prevalence of confirmed cases of permanent hearing
impairment, including congenital, late onset, and acquired cases.
Capture-recapture can correct for underascertainment of confirmed
cases. It does not discover cases that have not been confirmed.
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Methods |
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Case definition
Cases were children resident in the United Kingdom during 1998, born between 1 January 1980 and 31 December 1995 inclusive, with
confirmed permanent bilateral hearing impairment exceeding 40 dB HL
(hearing level) (average of pure tone thresholds at 0.5, 1, 2, and 4 kHz in the better hearing ear).
Ascertainment
Children were ascertained through professionals with
responsibility for the provision of audiological health care (n=473)
and education (n=434) to hearing impaired children. During 1998, professionals were asked by mail to complete a one page form for each
case known to them. Minimal data were requested to maintain anonymity
and maximise compliance: initials, sex, date of birth, home postcode,
average hearing level in the better ear, presumed age at onset of
hearing impairment, aetiology, other disabilities, parents' preferred
language, and details of the source. We sent one reminder to
non-responders after four months.
Capture-recapture
Capture-recapture techniques can estimate the size of populations
from restricted samples (fig 1), and hence can estimate the extent of
underascertainment in population surveys. Its use is valid when
four requirements are met: the population does not change between
compilation of the lists from different sources; cases from different
sources can be matched; each member of the population has the same
chance of inclusion in each list; and the sources are independent. The
first three requirements were met by conducting the ascertainment over
a short time span, by obtaining several identifiers for each case, and
by using distinct sources with obligatory responsibilities for all
hearing impaired children.
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Analysis
We applied capture-recapture using conventional formulas to
estimate the size of populations (fig 1).17 We used live birth statistics21 to convert counts of children into
prevalence rates per 1000 live births. We also calculated confidence
intervals for observed prevalences, assuming that counts obeyed Poisson probabilities, and for prevalences adjusted by capture-recapture using
conventional formulas.17
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Results |
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Response rate
Geographical coverage was comprehensive: professionals reported
children from every postcode area in the United Kingdom, and only two
of 122 postcode areas were not covered by professionals from both
health and education. Of the 473 health professionals contacted, 122 (26%) no longer had main responsibility for children in their
geographical area. There was considerable overlap of institutional
affiliation among the remainder, with the result that only 191 (54%)
individually provided data. Of the 434 education professionals
contacted, 23 had retired. Of the remainder, 295 (72%) provided data.
Validation of capture-recapture
The example in figure 1 documents the results of the validation
exercise and confirms the independence of the sources. The 95%
confidence interval of the estimated number of children with implants
embraces the true value overall and in 15 of 16 individual birth
cohorts (fig 2). Application of capture-recapture to the remainder
of the data was therefore justified.
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Prevalence
We received over 26 000 ascertainment forms. After we eliminated
duplicate notifications the number ascertained was 17 160 individual
children: 11 577 from health sources, 12 107 from education sources,
and 6524 from both. We calculated prevalence from observed counts and
from counts adjusted by capture-recapture (fig 3). Prevalence
declined for children in the oldest two cohorts (1981 and 1980), who
were aged from 16 to 18 years when the ascertainment was conducted.
Some would have left school and not been included in the education
list; some would have transferred from paediatric to adult hearing
services. Both effects violate the third requirement for
capture-recapture to be valid. Hence these cohorts were
excluded.
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Discussion |
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The prevalence of permanent childhood hearing impairment rises over a wider age range and to a higher plateau than has been reported previously. In our study data collection relied on notifications from professionals in health and education, not all of whom responded. However, geographical coverage was comprehensive, and the relation of our results to previously reported prevalence rates indicates that our methods of ascertainment were reliable.
Previous ascertainment studies included fewer children and a narrower range of cohorts and hence could not map the rise in prevalence across birth cohorts with the precision displayed in figure 3. The profile of the rise in prevalence with age has important implications for service delivery, which can be dealt with only when the variables underpinning the rise are understood. Three effects are likely to contribute.
Some children acquire impairment postnatally
Impairments
that are acquired, as distinct from progressive or of late onset, account for 4-9% of overall prevalence
7 15-16
and 7%
in the present study. Thus they explain only a small proportion of the rise.
Confirmation of impairment is delayed in some
children
Delayed confirmation of congenital cases may contribute
to the rise, particularly for lesser degrees of
impairment,
7 8 23
but if delay accounted for all of that
part of the rise not attributed to acquired impairment, and if
universal neonatal hearing screening identified all congenital
impairments, then the yield from screening would be close to the
aggregate prevalence in table 1. In fact, in the United Kingdom
the yield of children with bilateral hearing impairment
40 dB HL per
1000 live births has been reported as only 1.18 (34/28 890)23 and 0.94 (24/25 609),24
giving an aggregate yield of 1.06 (95% confidence interval 0.84 to
1.44). This is close to the overall prevalence in the youngest cohort in our study, and the upper confidence limit is below the aggregate prevalence (table 1). Thus it is unlikely that delayed
confirmation fully accounts for the unexplained portion of the rise.
Some inherited causes of hearing impairment manifest themselves
only postnatally
Many of the dominant genes for deafness are associated with late onset progressive hearing
impairment.
25 26
The protracted rise in the prevalence of
severe and profound impairments (fig 3) is more compatible with the
idea that some children have impairments of progressively increasing
severity than with the alternative that many congenital cases with
severe and profound impairments were not confirmed until several years
after birth.
The implementation of universal neonatal hearing screening should result in a well documented screening history for all children. That information, together with the results of genetic investigations in children with a newly confirmed diagnosis of permanent hearing impairment, would permit the rising profile of prevalence with age to be confirmed prospectively and would allow us to unravel the relative contributions of the three effects to the rise.
Conclusions
In the United Kingdom the prevalence of confirmed cases of
permanent childhood hearing impairment >40 dB HL has risen with age to
a significantly higher plateau than previous studies have estimated.
Prevalence at the plateau is at least as high as the observed value of
1.65/1000 live births and may approach the adjusted value of 2.05/1000
live births. The importance of these results rests on assumptions that
prevalence at the plateau will not change in the foreseeable future and
that the yield from universal neonatal hearing screening will remain
close to 1.06/1000 live births. If so, then for every 10 children with
a permanent bilateral hearing impairment >40 dB HL detected by
screening another five to nine children (50-90%) would manifest such a
hearing impairment by the age of 9 years. These additional children
would comprise some with congenital impairments who either miss
neonatal hearing screening or pass the screening despite having a
hearing impairment, some who acquire an impairment postnatally, and
others who manifest late onset or progressive impairments. Paediatric
audiology and associated services will need the capacity and skills to
identify and then confirm impairments in these children.
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Acknowledgments |
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We thank every professional who identified children and Mrs Margaret Eatough for facilitating the ascertainment in the education sector.
Contributors: All authors contributed to the design and interpretation of the study and reviewed the manuscript. Additionally HMF collected the data, DHM and AQS performed the analyses, and HMF and AQS drafted the manuscript. Danielle Betts and Sherie Holroyd assisted with the collection and entry of the data. HMF and AQS are guarantors.
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Footnotes |
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Funding: Medical Research Council with additional funding from
the National Lottery Charities Board through Defeating Deafness
The Hearing Research Trust.
Conflict of interest: None declared.
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References |
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| 1. | Conrad R. The deaf schoolchild: language and cognitive function. London: Harper and Row, 1979. |
| 2. | Wood D, Wood H, Griffiths A, Howarth I. Teaching and talking with deaf children. Chichester: Wiley, 1986. |
| 3. | Gregory S. Deaf children and their families. Cambridge: Cambridge University Press, 1995. |
| 4. |
Cheng AK, Rubin HR, Powe NR, Mellon NK, Francis HW, Niparko JK.
Cost-utility analysis of the cochlear implant in children.
JAMA
2000;
284:
850-856 |
| 5. | Mohr PE, Feldman JJ, Dunbar JL, McConkey-Robbins A, Niparko JK, Rittenhouse RK, et al. The societal costs of severe to profound hearing loss in the United States. Int J Technol Assess 2000; 16: 1120-1135. |
| 6. | Downs MP, Yoshinaga-Itano C. The efficacy of early identification and intervention for children with hearing impairment. Pediatr Clin N Am 1999; 46: 79-87[CrossRef][Medline]. |
| 7. | Fortnum H, Davis A. Epidemiology of permanent childhood hearing impairment in Trent region, 1985-1993. Br J Audiol 1997; 31: 409-446[Medline]. |
| 8. |
Van Naarden K, Decouflé P, Caldwell K.
Prevalence and characteristics of children with serious hearing impairment in Metropolitan Atlanta.
Pediatrics
1999;
103:
570-575 |
| 9. | National Institutes of Health. NIH recommends universal screening of infants for hearing impairment. Am Fam Physician 1993; 48: 521-522[Medline]. |
| 10. | Davis A, Bamford J, Wilson I, Ramkalawan T, Forshaw M, Wright S. A critical review of the role of neonatal hearing screening in the detection of congenital hearing impairment. Health Technol Assess 1997; 1(10): 1-176. |
| 11. | Dalzell L, Orlando M, MacDonald M, Berg A, Bradley M, Cacace A, et al. The New York State universal newborn hearing screening demonstration project: ages of hearing loss identification, hearing aid fitting, and enrolment in early intervention. Ear Hearing 2000; 21: 118-130[CrossRef][Medline]. |
| 12. | Department of Health. Piloting the introduction of universal neonatal hearing screening in England. www.doh.gov.uk/uhnspilots/index.htm (accessed 11 Jan 2001). |
| 13. | NHS Executive. Launch of pilot project to provide patients with digital hearing aids. www.doh.gov.uk/hearingaidproject/press0029.htm (accessed 11 Jan 2001). |
| 14. | Davis AC, Parving A. Towards appropriate epidemiological data on childhood hearing disability: a comparative European study of birth cohorts. J Audiol Med 1993; 3: 35-47. |
| 15. | Mäki-Torkko EM, Lindholm PK, Väyrynen MRH, Leisti JT, Sorri MJ. Epidemiology of moderate to profound childhood hearing impairments in Northern Finland. Any changes in ten years? Scand Audiol 1998; 27: 95-103[CrossRef][Medline]. |
| 16. | Uus K, Davis A. Epidemiology of permanent childhood hearing impairment in Estonia, 1985-1990. Audiology 2000; 39: 192-197[Medline]. |
| 17. | LaPorte RE, McCarty DJ, Tull ES, Tajima N. Counting birds, bees, and NCDs. Lancet 1992; 339: 494-495[Medline]. |
| 18. |
International Working Group for Disease Monitoring and Forecasting.
Capture-recapture and multiple-record systems estimation I: History and theoretical development.
Am J Epidemiol
1995;
142:
1047-1058 |
| 19. | Cormack RM. Problems with using capture-recapture in epidemiology: an example of a measles epidemic. J Clin Epidemiol 1999; 52: 909-914[CrossRef][Medline]. |
| 20. | Bloor M, Wood F, Palmer S. Use of mark-recapture techniques to estimate the size of hard-to-reach populations. J Health Serv Res Policy 2000; 5: 89-95[Medline]. |
| 21. | Office for National Statistics. Population trends, summer 1999. London: Stationery Office, 1999. |
| 22. | British Society of Audiology. Recommendations for pure-tone audiometry. Br J Audiol 1988; 22: 123. |
| 23. |
Watkin PM, Baldwin M.
Confirmation of deafness in infancy.
Arch Dis Child
1999;
81:
380-389 |
| 24. | Kennedy CR. Controlled trial of universal neonatal screening for early identification of permanent childhood hearing impairment: coverage, positive predictive value, effect on mothers and incremental yield. Wessex Universal Neonatal Screening Trial Group. Acta Paediatr Suppl 1999; 88: 73-75[CrossRef][Medline]. |
| 25. | Van Camp G, Smith RJH. Hereditary hearing loss homepage. www.uia.ac.be/dnalab/hhh (accessed 11 Jan 2001). |
| 26. |
Steel KP.
New interventions in hearing impairment.
BMJ
2000;
320:
622-625 |
(Accepted 25 May 2001)
Adrian Davis a Public Health and Clinical Section, MRC Institute
of Hearing Research, University Park, Nottingham NG7 2RD, b Department of Speech, Language, and Hearing
Sciences, University of Colorado, Boulder 80309-0409, Colorado, USA
Correspondence to: A Davis Adrian{at}ihr.mrc.ac.uk
The prevalence of permanent childhood hearing impairment of
40 dB HL or greater, and the probability that late onset and
progressive hearing impairment may be more prevalent than previously
indicated, has been discussed by Fortnum et al in their paper. There is
no estimate available of the number of children with "mild" (20-40 dB HL) bilateral permanent impairment or those with unilateral impairment, but current programmes that screen for hearing problems in
the newborn in the United States suggest that such impairment, identified by screening at birth, is at least as
prevalent.1
Screening hearing in newborns has been shown to be
efficient2 and cost effective,3 with a
sensitivity in the range of 80-90%, a false positive rate of <2%
4 5
and a positive predictive value of 17%. The proposed
costs of such screening in the United Kingdom are much lower than the
costs of the current infant distraction screen test,8 and
the cost per child identified as having bilateral permanent hearing
impairment is considerably less. There is little evidence that
screening all newborns for hearing raises anxiety among
mothers.6
The benefits of universal newborn hearing screening for children with
permanent hearing impairment are that early identification is
associated with better expressive and receptive language, speech, and
social and emotional development. Children who are identified before
the age of 6 months show substantial benefit in the first five years of
life, and there is some evidence that earlier enrolment in intervention
programmes is associated with better outcomes.7 A higher
level of expressive language in young children is linked with levels of
parental stress and better attachment as measured by emotional
availability.
8 9
However, if early identification and
intervention is not handled well at the service level, it can generate
anxiety and grief and bring about negative outcomes for the
family.10
The Department of Health has started a universal newborn hearing
screening programme in England, beginning with a pilot implementation with a hospital or clinic based protocol in 17 areas and a community based protocol in three areas. Concerns over the quality of services for the assessment of children's hearing for those referred from screening and of early intervention programmes for parents and their
children who have a confirmed permanent hearing impairment have been
raised. Family Friendly Hearing Services are being developed that have
three main characteristics. Firstly, service provision by all
professional sectors in a positive family friendly culture should
encourage "seamless" collaboration, responsiveness that meets the
family's real needs, and provision of appropriate information between
all agencies and for parents that enables families to make informed
choices about services for their children. Secondly, paediatric
audiology should exceed a minimum standard in terms of quality and
accessibility. Thirdly, there must be a culture of service evaluation,
including peer review, with an element of feedback from parents and
their children with impaired hearing. Data from screening and
assessments will be kept nationally on a database integrated with other
child services. This will facilitate the monitoring of later
development of permanent childhood hearing impairment and the
effectiveness of the screening programme.
The implementation team will rigorously assess access to and quality of
health and social care for these families, and outcomes of the
programme will be evaluated. Coordination of these services and support
options are key factors in the success of the programme, and
availability of the range of options would be severely restricted by a
lack of appropriately trained staff and resources. The aim is to detect
bilateral moderate to profound congenital permanent childhood hearing
impairment to enable high quality parent-child intervention services.
The advent of a national newborn hearing screening programme creates
the opportunity to help these children to develop their true potential,
provided that the training, resources, and coordination are made
available. We will need to monitor the outcomes of the children at
different ages to enhance the evidence base concerning the most
effective health, educational, and social interventions. There
continues to be a need to develop and implement more effective screening and case finding for school aged children (4-16 years) with
acquired and late onset hearing impairments that may negatively affect
their behaviour and educational achievement.
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References |
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| 1. | Dalzell L, Orlando M, MacDonald M, Berg A, Bradley M, Cacace A, et al. The New York State universal newborn hearing screening demonstration project: ages of hearing loss identification, hearing aid fitting, and enrolment in early intervention. Ear Hear 2000; 21: 118-130. |
| 2. | Davis A, Bamford J, Stevens J. Performance of neonatal and infant hearing screens: sensitivity and specificity. Br J Audiol 2001; 35: 3-15[Medline]. |
| 3. |
Stevens JC, Hall DM, Davis A, Davies CM, Dixon S.
The costs of early hearing screening in England and Wales.
Arch Dis Child
1998;
78:
14-19 |
| 4. | Yoshinaga-Itano C, Coulter D, Thomson V. The Colorado newborn hearing screening project: effects on speech and language development for children with hearing loss. J Perinatol 2000; 20: S132-S137[CrossRef][Medline]. |
| 5. | Kennedy C, Kimm L, Thornton R, Davis A. False positives in universal neonatal screening for permanent childhood hearing impairment. Lancet 2000; 356: 1903-1904[CrossRef][Medline]. |
| 6. | Watkin PM, Baldwin M, Dixon R, Beckman A. Maternal anxiety and attitudes to universal neonatal hearing screening. Br J Audiol 2000; 32: 27-37. |
| 7. | Moeller MP. Early intervention and language development in children who are deaf and hard of hearing. Pediatrics 2000; 106: E43. |
| 8. | Pressman L, Pipp-Siegel S, Yoshinaga-Itano C, Deas A. Maternal sensitivity predicts language gain in preschool children who are deaf and hard-of-hearing. J Deaf Studies Deaf Education 1999; 4: 294-304. |
| 9. | Pressman L, Pipp-Siegel S, Yoshinaga-Itano C, Kubicek L, Emde RN. A comparison of the links between emotional availability and language gain in young children with and without hearing loss. Volta Review 2000; 100: 251-277. |
| 10. | Hind S, Davis A. Outcomes for children with permanent hearing impairment. In: Seewald R, ed. A sound foundation through early amplification. Proceedings of the International Conference sponsored by Phonak Oct 1998, Chicago, Illinois, US. Staefa, Staefa, Switzerland: Phonak AG, 2000:199-212. |
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