1. Prevalence of permanent childhood hearing impairment Heather Fortnum Heather Fortnum B Med Sci, BM BS, DM MRC Institute of Hearing Research, Nottingham, UK

2. Heather Fortnum …is an epidemiologist working in Health Services Research for UK Medical Research Council...has always been interested in the impact of permanent hearing impairment on children...is excited by the current findings and their implications for Universal Newborn Hearing Screening

3. Impact on children Communication skills Educational attainment Quality of life

4. Early intervention leads to improved outcomes 1

5. Previous studies Relatively small No assessment of under-ascertainment

6. Capture-recapture No change in population Cases from different sources can be matched Same chance of being included in each data source Independent data sources

7. Sample from source 1 (m) Sample from source 2 (n) In common (c) Population (N ’ )

8. N = (m+1)(n+1) (c+1) - 1 95% c.i. = ± 1.96  Var(N) Var(N) = (m+1)(n+1)(m-c)(n-c) (c+1) 2 (c+2) Formulae Sources are independent if: p 1 x p 2 = p 12

9. Data source N of children Health professionals11577 Education professionals12107 Both 6524 Either17160 National Ascertainment Study

10. Observed prevalence (95% confidence intervals)

11. Adjusted prevalence (95% confidence intervals)

12. Prevalence by age Age (years) 024681012141618 Prevalence (per 1000 live births) 0.0 0.5 1.0 1.5 2.0 2.5 >40dB

13. Increase with age? Decrease with time?

14. Cohorts age inPrevalence per years1000 live births Trent Ascertainment 2 1985-1990 5-101.33 (95% ci 1.22-1.45) National Ascertainment 3 1985-19908-131.63 (95% ci 1.59-1.67) 1988-19935-101.44 (95% ci 1.41-1.48)

15. Conclusion The prevalence of permanent childhood hearing impairment continues to rise after birth over a wider age range than had previously been reported and reaches a higher plateau.

16. 1. Acquired impairments Usually due to bacterial meningitis or trauma Can occur at any age Contributes 7% of overall prevalence

17. 2. Delayed confirmation

18. 3. Late onset and/or progressive Many dominant genes for deafness in animal models are associated with late-onset progressive impairment. Van Camp G, Smith RJH. Hereditary Hearing Loss Homepage. WorldWide Web URL: http://dnalab-www.uia.ac.be/dnalab/hhh http://dnalab-www.uia.ac.be/dnalab/hhh Steel KP. New interventions in hearing impairment. Brit Med J 2000;320:622-625.

19. Conclusions The prevalence of confirmed permanent childhood hearing impairment (>40 dB HL) in the UK has risen with age to at least 1.65/1000 live births (and may be as high as 2.05/1000 live births) among children 9-years of age and older. If the current yield from Universal Neonatal Hearing Screening is sustained, then an additional 50-90% of children will remain to be detected in the post-natal years.

20. Reading list 1 - epidemiology 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. Karikoski JO, Martilla TI. Prevalence of childhood hearing impairment in Southern Finland. Scand Audiol 1995;24:237-241. 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 Van Naarden K, Decouflé P, Caldwell K. Prevalence and characteristics of children with serious hearing impairment in Metropolitan Atlanta. Pediatrics 1999;103:570-575.

21. Reading list 2 - epidemiology Uus K, Davis A. Epidemiology of permanent childhood hearing impairment in Estonia, 1985-1990. Audiology 2000;39:192-197. Hadjikakou K, Bamford J. Prevalence and age of identification of permanent childhood hearing impairment in Cyprus. Audiology 2000;39:198-201. Mencher G, Madriz JJ. Prevalence of sensorineural hearing loss in children in Costa Rica. Audiology 2000;39:278-283. Mencher G. Challenge of epidemiological research in the developing world: overview. Audiology 2000;39:178-183. Streppel M, Richling F, Walger M, von Wedel H, Eckel H. Epidemiology of hereditary hearing disorder in childhood. Scand Audiol 2000;29:3-9.

22. Reading list 3 - UNHS Watkin PM, Baldwin M. Confirmation of deafness in infancy. Arch Dis Child 1999;81:380-389. 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.

23. Reading list 4 - capture-recapture LaPorte RE, McCarty DJ, Tull ES, Tajima N. Counting birds, bees, and NCDs. Lancet 1992;339:494-495. 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. Cormack RM. Problems with using capture-recapture in epidemiology: An example of a measles epidemic. J Clin Epidemiol 1999;52:909-914. Bloor M, Wood F, Palmer S. Use of mark-recapture techniques to estimate the size of hard-to-reach populations. J Health Serv Res Pol 2000;5:89-95