Research shows that brain health is promoted by protecting our hearing and boosting it if necessary.

We are grateful to Associate Professor Grant Searchfield from the Hearing and Tinnitus Clinic and the Eisdell Moore Centre for research into hearing and balance disorders at the University of Auckland for his contribution.

Untreated hearing loss is linked to cognitive decline
  • Several studies have highlighted the contribution of hearing loss in mid-life to the risk of dementia in later life.
  • In fact, untreated hearing loss appears to be one of the largest modifiable risk factors for age-related decline in cognition and the risk of dementia.
  • Hearing loss is associated with cognitive decline independently of factors such as age, sex, and education that might explain this correlation.
Protecting our hearing
  • Age-related hearing loss is something that occurs for many of us to some degree as we age. It results in reduced audibility (how well our ear can hear a sound), poorer frequency resolution (how well our ear can distinguish between higher and lower pitched sounds), and changed loudness perception (how loud sounds seem to us).
  • In addition, some people damage their hearing throughout life, mainly from exposure to loud noise. The best medicine is to avoid damaging our ears in the first place.
Boosting hearing
  • Hearing aids are potentially an effective method to improve the cognitive health of older New Zealanders.

  • For example, in one large study in France, self-reported hearing loss was significantly associated with cognitive decline in 3670 persons aged over 65 followed over 25 years. The group using hearing aids had no cognitive decline on average compared with others their age, while those not using hearing aids did.

  • In another study from the United States, significant improvements in cognitive function were seen after 4 months of using a hearing aid for a group of 95 people with hearing impairment compared to 99 other people on a waiting list.

How hearing loss and boosting may impact on cognition
  • It has been said that “impaired vision cuts us off from the world of things but impaired hearing cuts us off from the world of people”. We know that social connectedness is important for brain health, so hearing impairment is likely to have a negative impact on our brains in part via its effects on our social lives.
  • Hearing loss also seems to have a direct impact. A study from the United Kingdom demonstrated that hearing aid use was associated with better cognitive function independent of social isolation.
  • Evidence from both animal and humans studies shows that environments lacking in rich sound can result in brain reorganisation. For example, areas of the temporal lobes of the brain that are important for semantic memory (knowledge of what things are including what they are called) and sensory integration (combing sound, sight, touch, and other sensory information to understand the world) show volume changes with hearing loss. These are areas that also change with cognitive impairment.
  • It may be that the mechanisms of improvement are primarily through increased audibility of sound so that the brain can use the information provided. Studies have also shown that some hearing-related brain changes can be reversed through stimulation.
  • A collaborative study between Auckland and Canterbury Universities funded by the Health Research Council of New Zealand has been under way for several years to investigate the effects of using hearing aids on cognitive function. The results are expected to be released in the final quarter of 2021 – be sure to look out for these in the New Zealand Dementia Foundation newsletter.
People living with dementia
  • People living with dementia and hearing impairment may also benefit from hearing aids, but they are of most benefit if they are used earlier in the dementia progression.
  • Later on in the dementia journey hearing aids may be too difficult for people to tolerate or to manage.
  • People living with dementia and hearing impairment benefit from other strategies to improve communication, such as reducing background noise, speaking directly, face to face, and using visual cues relating to what we are talking about, such as inviting someone to afternoon tea whilst holding out a cup of tea towards them, or suggesting it’s time for toothbrushing at the same time that we pick up a tube of toothpaste.
Communication
  • Hearing is very important, but good communication is not just about hearing. Our communication with other people can be enhanced or reduced by other factors, such as our ability to speak clearly, our knowledge of different languages and ways of talking, our ability to understand language at a brain level, and our social skills.
  • Speech language therapists have a very important role to play in helping people whose communication challenges come from neurological illnesses that affect speech and language, such as stroke.    
  • Supporting communication partners to listen carefully and speak clearly with each other is also something that can help, as can learning how to improve our social skills at any age.  
  • Using New Zealand Sign Language or other visual communication methods is also important for some people.
Take home messages
  • Communication (including listening to voices) is vital exercise for our brain.
  • Hearing loss is associated with increased risk of dementia.
  • There may be direct brain effects of hearing loss, but its effects on communication are also important – less communication with others means poorer brain health and well-being.
  • We should protect our ears from excessive noise at all ages – an ounce of prevention is worth a ton of cure.
  • If our hearing is becoming poor, we should visit an audiologist for a check-up.
  • If hearing aids are suggested, we should take the advice we are given seriously.
  • Good communication is not just about hearing but also about speech, language, visual cues, social context, and environment.