KidsAudiologist

How many deaf children are there?

Posted on: October 3, 2011

This is an article that I wrote on behalf of NDCS for the British Association of Teachers of the Deaf (BATOD) magazine. A slightly edited version was published in their September 2009 edition titled ‘The numbers game’. The question “how many deaf children are there in the UK?” is still frequently asked and in times of massive statutory service provision upheaval it seems fitting to revisit what we know (or perhaps don’t!) Perhaps a more accurate question would be to say “How many deaf children would you like there to be?”

It seems that what should be a relatively simple question is creating challenges across the country and for the professions for a variety of reasons; we’re all keen to know whether the now established newborn hearing screening programmes across the UK are working and if deaf children are being identified following the screen. Equally, Health Service commissioners want to know the number of care pathways they should be purchasing for their local population, and Local Authorities need to forecast the number of children in their area that are likely to need additional support from specialist hearing support services. In the current environment of restrictions in funding and changes in fund holders, more and more of us need to make outstanding business cases in order to expand, develop or prevent reduction in our services. A key element of this is knowing our population. It’s no longer good enough to say to purse holders ‘this is the way it’s always been done’. We now have to prove that this is the best way to go. So while those of us working at the coal face will continue, quite rightly, to rationalise resources towards those deaf children with the greatest need, NDCS will continue to lobby for greater resources to be made available from authorities and governments for those with a lesser, but none the less significant, need so that they too can benefit from the support available to other deaf children.

‘No national register of hearing impaired children exists for the UK, and accurate estimates of the prevalence of permanent childhood hearing impairment and of its profile across age and degree of impairment are unavailable.’(2)

NDCS has asked the respective governments how many deaf children there are and although we knew the answer would be ‘we don’t know’, we had to ask.  We can try and estimate the numbers of deaf children from a number of sources, all of which have their limitations:

BATOD survey

The BATOD survey has been an invaluable source of information about the numbers and educational settings of deaf children for a number of years. The survey in 2000 identified 28,184 deaf children known to hearing impaired support services in England. However, the information is dated and it is possible that the numbers of children identified could reflect the level of resourcing in a local authority. In particular it is possible that children with mild and unilateral were not included for example.

School census returns

In England, Wales and Northern Ireland the school census provides some information.  However this again has limitations. First it only includes those children placed at school action plus or with statements where HI is the main type of SEN. Thus many of the estimated 30-40% of deaf children with additional needs will be recorded under a different SEN category and not be included in this HI cohort. Deaf children placed at school action are also not counted. We also suspect from the wide variation in the percentage of children placed at school action plus or with statements that the number of children placed at School Action plus is related to the relative size of specialist services rather than the actual number. The census also excludes pre-school aged children, students attending FE colleges and pupils in private education.

Epidemiological research data

There are a few studies that record prevalence data in different areas/regions. We can then apply this data to estimates of the total population. Although our knowledge of prevalence rates has improved, particularly for babies since universal newborn hearing screening started, the figures for acquired and progressive deafness after this period is poorer. We know that the smaller the total child population the prevalence rates are applied to, the greater is the statistical unreliability of the estimate of deaf children. We also know from research that certain groups within the population are more likely to be deaf and often these groups will live and work in particular regions.(3,4) So, since prevalence rates tend to come from cohort studies in different regions we need to be cautious about applying them across the UK.

Degree of deafness

An additional complicating factor when trying to estimate numbers of deaf children is looking carefully at the definition used in the research. It has been common to talk about ‘significant’ deafness as bilateral and greater than 40 dBHL and most of the research targets these groups. There is now a lot of interest in the research community about permanent mild and unilateral deafness(5) and we’re starting to understand that these hearing losses are significant to a proportion of these children. However, only a couple of studies include these groups.

What the research tells us – for congenitally deaf children (born-with or acquired during/shortly after birth):

There is variation in prevalence depending on region but there seems to be a robust evidence base for the figures for congenitally deaf children with bilateral moderate or worse hearing loss in England. 1.0 per 1000 children are born with permanent bilateral deafness (>40 dBHL) and 0.64 per 1000 are possibly born with a unilateral deafness.(6) Described as “one of the few studies providing reliable evidence of the prevalence of this condition at birth” and “similar to published prevalence rates”. These figures are also quoted in the RCPCH 2004 report(7) where they are described as ‘current best estimates for prevalence’.

Screening protocols are generally designed to pick up babies with moderate of worse deafness. However, although some children with mild deafness do pass the screen level it is clear that some children are also identified this way.

What the research tells us – acquired deafness:

Prevalence data for acquired deafness during childhood is less robust but there are two recent publications of interest. Fortnum et al (2001) reported “Prevalence of confirmed bilateral PCHI (>40 dBHL) increases until the age of 9 years to a level higher than previously estimated. Relative to current yields of universal newborn hearing screening in the UK, which are close to 1/1000 live births, 50-90% more children are diagnosed with PCHI by the age of 9 years.” This study doesn’t look at children older than 9 and we know that acquired hearing loss happens in older children too. But this was the first time such a high acquired prevalence rate was identified. Previous research had suggested that between 11 and 16% were left to be identified following newborn screening. Since this data is for bilateral >40 dBHL deafness, there may be an assumption to make about acquired or progressive mild and unilateral losses too.

The recent Health Technology Appraisal of School Entry Screening (2007) looked at combined prevalence data from 3 cohort groups plus the data from the Trent study (all levels of hearing loss) and determined that the prevalence rate for bilaterals at age of school screen was 2.36-3.03/1000 (ave 2.69) and unilaterals 0.83-1.24/1000 (ave 1.04) giving a total of 3.73 per thousand children entering school with any degree of permanent deafness.

Number of deaf children

Given the range of prevalence data across studies and regions and the type of deafness being recorded a degree a caution is required when deriving estimates of the number of deaf children. This is illustrated in the recent Department of Health publication Transforming Services for Children with Hearing Difficulty and their Families: A Good Practice Guide (2008). This report states that for England  “At any one time, there are about 16,000-20,000 children aged 18 or under who have bilateral moderate, severe or profound hearing impairment, a high proportion of whom routinely use hearing aids, cochlear implants and other implantable devices to hear sounds”. The UK child population is about 20% above the figure for England. If we increased the Good Practice Guide’s estimate of deaf children by 20% then we could say that in the UK there are between 19,200-24,000 deaf children in this category. However, there is no methodology included to show what these figures are based on. The estimate of the number of deaf children depends on the prevalence rate selected and the age range that prevalence rate is applied. For example, for acquired deafness for those aged 0-9 years do we apply 0.5/1000 or 0.9/1000 and where in the 0-9 years do we start applying it?

NDCS Alternative Estimate

In summary, NDCS have used the 2006 mid year population estimates for the UK, applied stepped prevalence data for different age groups based on the research highlighted above and calculated a low and high prevalence range. At birth the prevalence used for combined bilateral and unilateral data is 2.1 per 1000. The minimum prevalence used for combined bilateral and unilateral data is 3.1 per 1000 and the maximum 3.9 per 1000 at age 18.

The research on acquired unilateral and mild deafness is less secure but using a similar strategy we get a range of between 18,800 – 22,400 children age 0-18 years.

Taken together we estimate that there are between 41,000 – 48,000 children in the UK aged 0-18 years with a permanent unilateral or bilateral, mild, moderate, severe or profound hearing loss.

Conclusion

So, this article actually raises more questions that it answers. As they say, you can prove anything with statistics! But are we right? Does it matter? And how might we go about finding out the real number of deaf children in this country?

References:

1. In this article the author uses the term ‘deaf’ and ‘deafness’ to mean all types and levels of permanent hearing loss.

2. Prevalence of permanent childhood hearing impairment in the United Kingdom and implications for universal neonatal hearing screening: questionnaire based ascertainment study; Heather M Fortnum, Quentin Summerfield, David H Marshall, Adrian C Davis, John M Bamford, BMJ 2001; 323:536

3. Fortnum, H. and Davis, A. Epidemiology of permanent childhood hearing impairment in Trent Region, 1985-1993, British Journal of Audiology, 1997, 31, 409-446

4. Bradford study (prevalence rate was 4.69/1000 compared with non-Asian children of 1.38/1000 births), Dr Gill Parry, published in the BACDA Newsletter October 1996, p25-29

5. Unilateral hearing loss in infants, editorial, British Journal of Audiology, 2007

6. Report of the Evaluation of the first phase of implementation of the NHSP, Revised 2005

7. Children’s Audiology Services – A Multidisciplinary Review in Partnership with the NHSU, Hall, 2004

8. Current practice, accuracy, effectiveness and cost-effectiveness of the school entry hearing screen, Health Technology Assessment 2007; Vol. 11: No. 32

9. Transforming Services for Children with Hearing Difficulty and their Families: A Good Practice Guide, DH, 2008

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