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Outcomes for wearers of hearing aids and improving hearing aid technology

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  1. Outcomes for wearers of hearing aids and improving hearing aid technology Harvey Dillon NAL CRC Hear Denis Byrne Oration Canberra, 2008.

  2. Who benefits from hearing aids? What can hearing aids do for people with hearing loss? How can we make hearing aids work better? Dillon, NAL

  3. The bits of this talk …. • Who’s got hearing aids • Who should have hearing aids • Who’s got hearing aids but shouldn’t • How people misjudge their hearing • Why hearing aids are sometimes useless • How technology is changing candidacy • Hearing aids of the future • What we should do differently now Dillon, NAL

  4. UK USA Davis (2003) Kochkin (1992) Who is using hearing aids?Of those with >25 dB 4FAHL in better ear Use 23 % Australia Don’t have 67 % Don’t use 10 % Source: Blue Mountains Study (Mitchell, Hartley et al) Dillon, NAL

  5. Percentage penetration of hearing aids Mitchell (2002) Dillon, NAL

  6. Hearing loss in the future Sources: ABS series B Sth Aust population study Possible further increase from: Personal stereo use ↑ Rock music  ↑ Power tools  ↑ Premature baby survival  ↑ And decrease from: War exposure ↓ Manufacturing ↓ Rubella epidemics ↓ Dillon, NAL

  7. Growth in people with hearing loss (>25 dB 4FAHL better ear) Blue squares = 2.5% compound growth Over 55 years Over 65 years Source: Hartley & Dillon, unpublished data Dillon, NAL

  8. Growth in OHS voucher numbers Blue squares = 9% compound growth Dillon, NAL

  9. Penetration:Hearing aid owners as a proportion of those with >25 dB 4FAHL better ear OHS vouchers: 9% OHS vouchers: 5% Hearing impaired growth: 2.5% Dillon, NAL

  10. Conundrum • Older people more likely to need a hearing aid • Younger people more likely to adapt well to using a hearing aid • Alberti (1977); Brooks (1985) Implication We need to know who will benefit from a hearing aid so those people get them as soon as possible Dillon, NAL

  11. What should penetration be?Who does benefit from a hearing aid? Dillon, NAL

  12. Should be possible to find the minimum aidable hearing loss Experiment To determine the minimum hearing loss for which clients will receive benefit from hearing aids. • Previous research has not indicated a close relationship between benefit and hearing thresholds. • Some people with very mild losses are being fitted in the current scheme. • It is extremely unlikely that people with normal hearing would benefit from hearing aids. Dillon, NAL

  13. Procedure • 400 clients sampled from OHS voucher database • 41,521 new clients fitted Feb to Sept, 2004 • Audiometric and other details obtained from selected clients’ files • Questionnaire sent to selected clients • International Outcome Inventory for Hearing Aids • Plus 6 purpose-designed questions • Selected clients followed up by phone or additional mail to get a high response rate (effectively 86%) Dillon, NAL

  14. Hearing loss characteristics of study sample Dillon, NAL

  15. Usage of hearing aids Dillon, NAL

  16. Factor analysis of questionnaire International Outcomes Inventory for Hearing Aids Dillon, NAL

  17. Composite benefit Composite difficulty Vision Factor analysis of questionnaire International Outcomes Inventory for Hearing Aids Dillon, NAL

  18. Simple correlations • People who more strongly wanted to get hearing aids: • Use them more (Q3) • Benefit from them more (Q4) • Say they are worth it (Q6) • Improve their enjoyment of life by using them (Q9) • Would replace their hearing aids if lost (Q10) • People who had the most difficulty unaided: • Use their hearing aids more (Q3) • Benefit from them more (Q4) • Say they are worth it (Q6) • Improve their enjoyment of life by using them (Q9) • Would replace their hearing aids if lost (Q10) Dillon, NAL

  19. Use + Composite Benefit Benefit + Satisfaction + QOL Dillon, NAL

  20. Composite benefit for different daily usage High use goes with high benefit and vice-versa Dillon, NAL

  21. What might account for variation in benefit? • Hearing loss • Age • Gender • Type of hearing aid • Difficulty listening unaided • Original desire to get hearing aids • Visual ability Dillon, NAL

  22. Difficulty hearing unaided and wish to get hearing aids Unaided difficulty related to wish to get hearing aids Dillon, NAL

  23. Difficulty listening unaided Need + Desire to get hearing aids Dillon, NAL

  24. Only self-assessed need predicts outcomes Relationship between predictors and outcomes Dillon, NAL

  25. Effect of hearing loss on benefit Dillon, NAL

  26. Effect of hearing loss on benefit Dillon, NAL

  27. How is composite benefit related to need? Dillon, NAL

  28. Benefit versus need Dillon, NAL

  29. “I don’t wear my hearing aids – never did. I don’t know why they gave them to me.”- Participant 1-089 Dillon, NAL

  30. Benefit for different degrees of hearing loss Dillon, NAL

  31. Benefit for different hearing aid types Dillon, NAL

  32. Benefit for top-up and free-to-client Dillon, NAL

  33. Are outcomes affected by the provider the client goes to? Dillon, NAL

  34. Contractor C clients get less benefit, on average Benefit for different contractors P=0.0004 Dillon, NAL

  35. Why? Dillon, NAL

  36. 8 dB Contractor C clients are less deaf Hearing loss for different contractors Dillon, NAL

  37. 0.8 scale points Contractor C clients express less need for assistance Need strength for different contractors Dillon, NAL

  38. Which: hearing loss or need? • Allow for differences in hearing loss  difference in benefit remains (p=0.002) • Allow for the differences in need  difference in benefit disappears (p=0.33) Dillon, NAL

  39. Contractor C Benefit vs Needs applies to all contractors Contractors A, B, D and E Dillon, NAL

  40. Implication Benefit is much more strongly determined by need than by hearing loss. “Need” = difficulty listening unaided + desire to get hearing aids in first place Dillon, NAL

  41. Why don’t people with hearing loss acquire hearing aids? “My hearing loss is not bad enough to need them” (Kochkin, 1993) • beliefs about difficulties they are having • beliefs about hearing aid likely benefits • beliefs about emotional consequences of wearing hearing aids • beliefs about practical issues (expense, complexity, manipulation) Dillon, NAL

  42. Health belief model People act rationally, in their best interests, based on their beliefs Difficulties experienced: frequency, severity Self-image Hearing aid effectiveness Effect on others’ view Ability to manage Hearing loss Cost Inconven-ience Dillon, NAL

  43. Self-image Effect on others’ view Hearing aid effectiveness Ability to manage Difficulties experienced: frequency, severity Cost Inconven-ience Hearing loss Health belief model People act rationally, in their best interests, based on their beliefs Dillon, NAL

  44. Difficulties experienced: frequency, severity Self-image Hearing aid effectiveness Effect on others’ view Ability to manage Hearing loss Cost Inconven-ience Health belief model People act rationally, in their best interests, based on their beliefs Dillon, NAL

  45. I don’t want hearing aids Dominant community belief Acquire hearing aids anyway Tell everyone “Prove” that hearing aids don’t work Circle of negative beliefs positive Hearing aids don’t work Dillon, NAL

  46. Expectations and benefit • Higher expectations  greater use and benefit (Jerram & Purdy, 2001) • Higher expectations  higher benefit (Cox & Alexander). Outcomes Use, benefit Satisfaction Expectations Dillon, NAL

  47. 125 250 500 1k 2k 4k 8k 0 20 40 60 Frequency (Hz) 80 100 120 Hearing threshold (dB HL) What can a hearing aid actually do? • Amplify soft sounds • Emphasise frontal sounds 35 dB 4FA HL Dillon, NAL

  48. Amplifying soft sounds Speech at 55 dB SPL Speech intelligibility index = 0.45  Percent words in sentences correct = 93% Dillon, NAL

  49. Amplifying speech (quiet; no reverberation) People with mild to moderate loss can cope reasonably well in quiet. Dillon, NAL

  50. 2. Speech in noise and reverberation Noise and reverberation both usually have biggest effect on low frequencies Dillon, NAL