Can hearing aids prevent dementia?

1. Can hearing aids prevent dementia? Piers.dawes@manchester.ac.uk

2. Dementia • Symptoms: memory loss, mood changes, problems with communication and reasoning • Associated with age, but not necessarily ‘natural’ aging; caused by diseases of the brain (e.g. Alzheimers)

3. Dementia: high prevalence www.alzheimers.org.uk

4. Aging EU population

5. Increasing numbers with dementia www.alzheimers.org.uk

6. Cost and prevention • Profound impact on individual and family • Progressive, no cure • £23 billion pounds (£8 billion in social care) • Delay by 2 years  reduce prevalence by 13% • Delay by 5 years  reduce prevalence by 33% Vickland, V., Morris, T., Draper, B., Low, L., & Brodaty, H. (2012). Modelling the impact of interventions to delay the onset of dementia in Australia. A report for Alzheimer’s Australia: Alzheimer's Australia.

7. Prevention? • Lower prevalence in younger generation 1989-1994 UK adults >65 years 8.3% 2008-2011 UK adults >65 years 6.5% Matthews, F. E., Arthur, A., Linda E Barnes, L. E., Bond, J., Jagger, C., Robinson, L., et al. (2013). A two-decade comparison of prevalence of dementia in individuals aged 65 years and older from three geographical areas of England: results of the Cognitive Function and Ageing Study I and II. The Lancet, Published online July 16, 2013. • (low quality) evidence that • Diabetes, hyperlipidemia & smoking are associated with increased risk • Mediterranean-type diet, folic acid intake, low/moderate alcohol intake, cognitive activities and physical activity are associated with decreased risk Daviglus, M. L., Bell, C. C., Berrettini, W., Bowen, P. E., Connolly, E. S., Cox, N. J., et al. (2010). National Institutes of Health State-of-the-Science Conference statement: preventing alzheimer disease and cognitive decline. Annals of internal medicine, 153(3), 176-181.  Urgent need for research into prevention

8. Could treating hearing loss reduce dementia?

9. Lindenberger, U., & Baltes, P. B. (1994). Sensory functioning and intelligence in old age: a strong connection. Psychology and aging, 9(3), 339.Baltes, P. B., & Lindenberger, U. (1997). Emergence of a powerful connection between sensory and cognitive functions across the adult life span: a new window to the study of cognitive aging? Psychology and aging, 12, 12-21. Sensory losses associated with cognitive decline • Berlin aging study • 687 people aged 25-103 • Intelligence (14 tasks), • Vision and hearing acuity • Sensory function 94.7% age-related & 12.6% age-independent variance

10. Hearing loss associated with increased risk of dementia Lin, F. R., Metter, E. J., O'Brien, R. J., Resnick, S. M., Zonderman, A. B., & Ferrucci, L. (2011). Hearing loss and incident dementia. Archives of Neurology, 68(2), 214.

11. Hearing loss and dementia • HL is associated with cognitive decline and an increased risk of dementia. It is unknown whether these associations represent i) a ‘common cause’ (such as vascular or neural changes that have independent effects on both cognition and sensory performance) and/or ii) auditory deprivation (sensory deprivation impacting on cognition either directly via impoverished input or via knock-on effects of hearing loss on social isolation and depression)

12. Hearing aids prevent dementia? • If deprivation  cognitive decline and dementia • Remediate deprivation (e.g. by providing hearing aids)  slow cognitive decline and prevent dementia?

13. Impact of hearing aids on cognition • Study 1: UK Biobank • Associations between hearing aid use and cognition; cross-sectional analysis • Study 2: Epidemiology of hearing loss study • Comparison of cognitive outcomes in HA users vs non-users in a 20 year longitudinal data set

14. Study 1. • Model associations between hearing and cognition in the large UK Biobank data set. • Association of poor hearing with poor cognitive performance would be consistent with either the ‘common cause’ or deprivation hypotheses. • But if auditory deprivation contributes to cognitive decline, then one would expect that for equivalent levels of hearing loss, use of hearing aids would be associated with better cognitive performance. • Role of social isolation and/or depression

15. Participants: A subset of the UK Biobank resource (N= 164,770) • Hearing: Digit triplet test

16. Digit triplet test (better-ear 50% speech recognition threshold)

17. Cognitive tests 1. Fluid IQ 2. Reaction time Combine  cognitive function 3. Memory

18. Hearing aid use: self report question "Do you use a hearing aid most of the time?” • Social isolation: self report question "Do you often feel lonely?" and number of social activities • Depression: "Over the past two weeks, how often have you felt down, depressed or hopeless?" and "Over the past two weeks, how often have you had little interest or pleasure in doing things?“

19. Structural equation modelling • Model and test causal relations Hypothesis variables and relations in a model do the data fit the hypothetical model?

20. Structural equation modelling: • is the association between hearing loss and cognition may be mediated by hearing aid use, social isolation and/or depression? • Controlled: age, sex, general health and socioeconomic status

22. HEARING LOSS AND COGNITIVE DECLINE HEARING LOSS HEARING AID USE SOCIAL ISOLATION DEPRESSION COGNITION Solid line = association Dashed line = no association

23. Summary Study 1 • HA use associated with better cognition (effect of HA use, or smarter people use HA?) • If HA have a positive effect on cognition, it is unlikely to be via reduced social isolation/depression • Need longitudinal data

24. Study 2: Long-term outcome of hearing aid use • Among those with hearing loss, compare cognitive performance in hearing aid users versus non-users • Hypothesis: hearing aid users should have better cognition, lower incidence of cognitive impairment

25. Study 2. EHLS • Longitudinal cohort • Epidemiology of hearing loss (EHLS) • Subset of sample selected if they had hearing loss • Compare hearing aid users with non-users • Control for potential confounds (age, health, gender, hearing loss)

26. 5 years before baseline No difference: gender, income, education level, ethnicity, general health Poorer hearing Baseline Baseline + 5 years Baseline + 11 years

27. Cognitive measures Cognitive performance • Mini mental state • Trail making A&B • Digit-symbol substitution • Auditory verbal learning test • Verbal fluency test Incident cognitive impairment • Doctor-diagnosed alzheimers, or • Fail Mini mental state exam

29. Summary • Study 1: hearing aid users had better cognitive performance. Supports possible impact of HA in improving cognition • Study 2. No differences in cognitive performance or incidence of impairment between hearing aid users and non-users. This is not supportive of a robust effect of hearing aid use as being protective against cognitive decline.

30. Why discrepancy? • Older US sample (but similar results in younger sample) • Different system for HA provision in US (but no difference in education level or income) • Lower power US sample size (but trend for worse performance by HA users) • Study 2 stronger design (more believable)

31. Hearing aids and living well • Dementia: cognitive impairment severe enough to impact on daily functional ability • Hearing loss may exacerbate disability • Hearing aids may decrease disability, thereby delaying the point at which ‘dementia’ may be diagnosed • Hearing aids may not prevent underlying brain pathology, but may improve quality of life and increase ‘healthy’ life span

32. Future • Intervention studies

33. Thanks Manchester Kevin Munro, Richard Emsley Nottingham Mark Edmondson-Jones, Heather Fortnum, Abby McCormack Cincinnati Dave Moore Wisconsin Karen Cruickshanks, Mary Fischer, David Nondahl, Barbara Klein, Ron Klein