Results of the ENHANCE study after 3 years of hearing aid use

Evaluation of Hearing Aids and Cognitive Effects (ENHANCE) study 3-year outcomes suggest hearing aid use may support longer-term cognitive health.

New results, just published in the journal of Frontiers in Aging Neuroscience, compared the cognitive performance of a group of new hearing aid users and a group of non-users over 3 years at 18-month intervals.

The hearing aid user group were clients of an audiology clinic and the non-hearing aid user group were participants of the Australian Imaging Biomarkers and Lifestyle (AIBL) Flagship Study of Aging. Participants were all aged 60 years or over.

  • After 3 years, the hearing aid user group showed relative cognitive stability while the non-hearing aid user group declined significantly.
  • The non-hearing aid user group showed significantly greater worsening of mean scores per year relative to the hearing aid group on all cognitive subtests but one, where the trend was the same but not statistically significant.
  • This outcome occurred despite a significantly faster rate of hearing loss over the follow-up period for the hearing aid user group.
  • When differences in education levels between participants were considered, the overall results did not change.

Hearing aid use may be an important public health strategy for delaying cognitive decline and thus reducing or slowing the onset of dementia.

Cognitive aging

The process of aging involves cognitive aging – the brain ages along with the rest of our body. This process begins as early in life as our twenties.1 The rate of cognitive aging can vary significantly between different people. Sometimes there can be a bigger difference in rates of cognitive aging for people of the same age than between people of different ages.

Cognitive aging does not affect the ability of most people to carry out their daily activities, but often people notice their memory is not as sharp as it used to be, that switching between tasks requires more effort, or that they are slower in doing some thinking tasks.

Hearing loss and cognitive decline

Many people don’t know that hearing loss is associated with an accelerated rate of cognitive decline, which raises the risk of dementia for people with untreated hearing loss.

Research indicates that the rate of cognitive decline increases with increasing severity of hearing loss. The population risk for people with mild hearing loss is almost double that of a person with normal hearing. For people with severe hearing loss, the risk is almost 5 times greater than for those with normal hearing.2

Up to 40% of dementia cases are thought to be preventable. Of the 12 potentially modifiable risk factors identified by the Lancet Commission on Dementia, hearing loss is the largest contributor, or most significant potentially modifiable risk factor.3-4

What could explain the link between hearing loss and cognitive decline?

Although it is unknown what the link between hearing loss and cognitive decline is, several theories propose explanations. One theory suggests that parts of the brain that are no longer or less stimulated by sound degenerate, causing changes in brain structure and function.5

A second theory is that when there is a hearing loss, greater cognitive effort and more of the brain is used to process speech, ‘robbing’ other parts of the brain from other functions, and thereby decreasing cognitive performance in other areas.6

The third theory suggests that reduced environmental stimulation, difficulties with communication, and subsequently lower social participation may contribute to psychological effects including loneliness and depression, leading to changes in brain structure and function.7

As hearing loss can occur many years, or even decades, before dementia onset, there may be a window of opportunity to address one or more of the proposed modifiable mechanisms of dementia development associated with untreated hearing loss.

Promoting cognitive health and healthy aging with hearing aid use

In addition to greater dementia risk, hearing loss is associated with a higher risk of falls8, more frequent hospitalizations and use of medical services9, depression10, and even a greater risk of death11. Many people are unaware of this.

Action can be taken to assist with maintaining and protecting our cognitive, physical, and mental health. Being able to hear well and maintain effective communication and connections with others will not only likely promote cognitive health but also overall healthy aging, maintenance of function, and better quality of life. Lacking social connection has been shown to be as dangerous as smoking up to 15 cigarettes a day!12

Preventative action is best taken before the onset of hearing loss-related adverse outcomes and when the brain is still flexible, to facilitate the brain re-wiring that physiological studies have shown occurs when hearing is restored.

To learn more on this topic, we invite you to listen to a podcast with Professor Julia Sarant and read an article published by the University of Melbourne Pursuit.

References:

1.  Salthouse, T.A. (2010). Major issues in cognitive aging. Vol. 49, New York, U.S.: Oxford University Press.

2.  Lin, F.R., et al. (2013). Hearing loss and cognitive decline in older adults. JAMA Internal Medicine.

3. Livingston, G., et al. (2017). Dementia prevention, intervention, and care. The Lancet, 390(10113): 2673-2734.

4.  Livingston, G. et al. (2020). Dementia prevention, intervention, and care: 2020 report of the Lancet Commission. The Lancet, 396(10248): 413-446.

5.  Oster, C. (1976). Sensory deprivation in geriatric patients. Journal of the American Geriatrics Society, 24(10): 461-464.

6.  Baltes, P. & 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(1): 12.

7.  Fulton, S.E., et al. (2015). Mechanisms of the hearing–cognition relationship. Seminars in Hearing, 36(3): 140-149.

8.  Jiam, N.T.L., Li, C. & Agrawal, Y. (2016). Hearing loss and falls: A systematic review and meta‐analysis. The Laryngoscope, 126(11): 2587-2596.

9.  Genther, D.J., et al., (2013). Association of hearing loss with hospitalization and burden of disease in older adults. JAMA, 309(22): 2322-2324.

10.  Lawrence, B.J., et al. (2019). Hearing loss and depression in older adults: A Systematic Review and Meta-analysis. The Gerontologist, 60(3): e137-e154.

11.  Tan, B. et al. (2021). Associations of hearing loss and dual sensory loss with mortality: A systematic review, meta-analysis, and meta-regression of 26 observational studies with 1 213 756 participants. JAMA Otolaryngology–Head & Neck Surgery.

12.  Holt-Lunstad, J., Robles, T.F. & Sbarra, D.A. (2017). Advancing social connection as a public health priority in the United States. American Psychologist, 72(6): 517.