02 Jun 2020

DEMENTIA LINK

Deafness is now known to be the largest modifiable risk factor for developing dementia.

Difficulty hearing can impair brain function by keeping people socially isolated and inadequately stimulated by aural input. The more challenging it is for the brain to process sound, the more it has to work to understand what it hears, harming its ability to perform other cognitive tasks. Memory can also be affected as information that is not heard clearly impairs the brain’s ability to remember it.

The Baltimore longitudinal study of ageing was started in 1958 by the National Institute on Ageing to track various health factors in thousands of men and women. One of the most compelling findings from this study is that those with hearing loss lose more than an additional cubic centimetre of brain tissue each year compared with those with normal hearing.

The below image shows the difference in average slopes of RAVENS gray matter, mapped between those with hearing impairment versus normal hearing. Blue/green are regions in which individuals with hearing impairment compared to those with normal hearing had a higher rate of gray matter decrease. Colour bars denote regression coefficient t-values (regression coefficient/standard error).

From: Association of Hearing Impairment with Brain Volume Changes in Older Adults. F.R.Lin et al (2014). In NeuroImage.

Hearing loss reduces the incidence of dementia.

Preventing or treating hearing loss in midlife has the potential to diminish the incidence of dementia by 9 percent according to an international analysis published in The Lancet in 2017. The study noted that this impact exceeds that of smoking, high blood pressure, lack of exercise and social isolation.

Below is a Life-course model of the contribution of modifiable risk factors to dementia.

From: ‘Dementia prevention, intervention, and care.’ G.Livingston et al. (2017). In The Lancet. (Numbers are rounded to nearest integer. Figure shows potentially modifiable or non-modifiable risk factors.)

Unfortunately we’re not only talking about moderate or severe hearing loss here. In 2019 a team from Columbia University Irving Medical Center found an independent association between cognition and hearing loss even below normal clinical thresholds.

So what to do?

Thankfully, knowing a problem exists means we are well on our way to solving it. First of all, take care of your hearing – don’t over-expose yourself to noise and if you or those around you think you might have a hearing loss, get it checked out and addressed as soon as possible.

Second, if you are responsible for other people’s hearing, perhaps as a health and safety specialist, occupational hygienist or responsible manager in an industry that produces workplace noise over 80dB, directly address your risks immediately. It is a legal duty to manage noise at work but Eave is here to help you get it right as cost-effectively as possible.

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