Recent Highlights From World Leader on Untreated Hearing Loss and Cognitive Decline
Recently, I had the pleasure of attending a keynote presentation in Sydney by Professor Frank Lin of John Hopkins University. He led the research team that published ground-breaking research in 2011 which, for the first time, showed the clear links between untreated hearing loss and dementia.
If you’ve been to one of my seminars or read my book Catching the Mind Robber – A Summary, you may be familiar with some of his work. It was really helpful to learn more of the background to his research including some of the nuances of what has been published and what new research is in the pipeline. I also found fascinating his findings in related areas such as untreated hearing loss and depression.
According to Professor Lin, projections estimate that the prevalence of dementia is expected to double every 20 years, to the point that one in every thirty Americans will have dementia by 2050. That’s one in thirty of the total population. What sparked much of the work and focused interest on dementia and untreated hearing loss was discovering that hearing impairment is independently associated with a 30-40% rate of accelerated cognitive decline.
Two major independent studies found that a 25dB (roughly 25%) shift in hearing levels was equivalent to nearly seven years of ageing on cognitive scores in older adults. Hence, a 50dB shift would, on average according to the studies, result in an increase in cognitive age of around 14 years. This would give a 59-year-old person the cognitive abilities of a 73-year-old. This is quite significant and very concerning. The two studies repeated independently yielded, essentially, identical results.
Between 1990-1994, 639 participants (aged 39-90 years) entered an intensive study on ageing. None had dementia at the start of the 12-year longitudinal study. Using a rigid definition of dementia, following annual checks over a 12-year period, subjects had a 200%, 300% or 500% increased risk for dementia depending on whether their hearing loss was mild, moderate, or severe, respectively. In cases of hearing loss, they also found up to a 40% loss of matter in the areas of the brain associated with speech, language, memory and attention. Similar results have been observed elsewhere which is further evidence to suggest that taking action early on hearing loss is advisable.
Professor Lin’s current work is focused on the impact that consistent hearing aid use has on the slowing and/or reversal of cognitive decline. This major study won’t be published until 2022/2023.
A recent study using functional MRI showed structural and functional changes in the brain following 12 months’ full-time hearing aid use. Another showed that hearing aid owners experienced a 75% reduction in dementia risk. It is anticipated that Professor Lin’s research will support this growing body of evidence linking hearing and brain health.
Whilst it could be easy to feel discouraged about hearing loss and its link with dementia, I would urge readers to feel particularly encouraged about the positivity of treating hearing loss early.
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