Dementia is a term that is used to describe many diseases that affect your memory , personality, mood and thinking. Dementia is diseases such as, Alzheimer’s, Parkinson, Lewy body, and vascular dementia to name a few.
Worldwide an estimated 50 million people suffer with dementia. However, that number is projected to rise to 152 million by 2050, rising especially in those low income countries.There are 12 main risk factors for dementia, and modifying them can prevent or delay dementia by 40% . One of these risk factors is hearing loss
So what is hearing loss? Hearing loss is the loss of hearing, there are 3 types of hearing loss:
Conductive, which involves the outer or middle ear. This happens when sound waves are blocked or can’t pass through the outer or middle ear to the inner ear. It is caused by ear infections, build up of earwax ect.
Sensorineural, which involves the inner ear. Occurs when there is damage done to the inner ear or the auditory nerve. This is caused by aging, loud noises, or head trauma.
Mixed, which is a mix of the two. This involves a combination of both, so there is damage both the outer/middle ear and the inner ear/ auditory nerve. This is caused when someone with sensorineural hearing loss gets an ear infection or trauma.
•There are many theories as to why hearing loss causes dementia, although the exact mechanisms are still being studies, here are some ways in which hearing loss can contribute to the development of dementia.
One of the ways hearing loss and dementia could be linked is through our blood system, certain types of dementia , especially vascular dementia, is caused when the blood flow to the brain is restricted, this causes damage to the brain cells. Recent studies show that the parts of the brain that are responsible for processing sounds are particularly vulnerable to damage.
Another theory is that people with hearing loss increase cognitive efforts , in attempts to hear and understand conversations. This can potentially lead to cognitive overloads, where the use more of brains resources to help them process sounds, at the expense of other cognitive processes such as memory. Over time, this can lead to brain atrophy and cognitive decline.
Hearing loss can make it difficult to have conversations and maintains friendships. This can lead to isolation and depression. Depression is another risk factor of dementia , and can also cause cognitive decline.
Furthermore, hearing loss can decrease cognitive reserve. Which is the brains ability to whit-stand neurological damage due to aging and/or disease. An individuals cognitive reserve is built up over their life, through socializing, education ect. When hearing loss isn’t treated with hearing aids it can cause social isolation which in turn decreases cognitive reserve.
In 2021, a team of researches at the University of California, Irvine, worked with mice engineered to mimic the symptoms of Alzheimer's disease, researchers discovered that deafness resulted in a higher deposit of b-amyloid plaques in the hippocampus and auditory cortex.
The special thing about these mice, is that they modified the genes of so that the mice could produce the human version of the B-amyloid protein.
Analyzing the underlying process by elucidating the pattern of gene expression, showed that decreased regulation in the gdf1 gene led to lower growth factor, GDF1.GDF1 may help with synaptic dysfunction and cognitive decline. “These finding indicate hearing loss could promote pathological changes in Alzheimer's disease by inhibiting GDF1 signal pathway.”
Here are a few studies that show the clear risk hearing loss has on developing dementia : A study of 6500 people with a mean age of 59.4 found that hearing loss decreases cognition .Another study of 200 people, without baseline cognitive impairments, with a follow up of 20 years found that midlife hearing impairments caused a loss of the temporal lobe . Including the hippocampus, which is involved in memory, learning and emotion, as well as loss of the entorhinal cortex, which is gateway for information entering and leaving the hippocampus. Lastly, the Aging and cognitive health evaluation in elders ( ACHIEVE) trial showed a decrease of 47% in cognitive decline. Experts are concerned that hearing impairments are the most important risk factor, and has a 78% consitney of association over 18 studies.
There are some protective measures those with hearing loss can use to prevent their condition from worsening, the most common one is hearing aids. Hearing aids are small devices that help people with hearing loss, they are installed during cochlear implant surgery . They improve hearing and speech in those that have hearing loss.Hearing aids work by amplifying sound. A 25-year study including 3700 adults over 65 revealed a higher risk of dementia in those with hearing impairments who do not wear hearing aids.According to a survey completed by 2040 Americans over the age of 50, using hearing aids improved delayed recollection less. This demonstrates how protective hearing aids are.
Comments