Longevity Briefs: Hearing loss can make dementia worse

Longevity briefs provides a short summary of a novel research, medicine, or technology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.

Why is this research important: Auditory cognitive processing takes place in the medial temporal lobe, which also plays important role in dementia pathology, which suggests that there might be a link between hearing loss and dementia. Therefore it is highly probable that hearing loss can worsen dementia symptoms or even cause it in the first place.

What did the researchers do: In this review article, researches have proposed 4 different mechanisms on how hearing loss causes dementia, based on present evidence.
Fist one suggests that common pathology (like Alzheimer’s disease or vascular disease) affect cochlea and ascending auditory pathway, which in turn affects the cortex.
The second mechanism proposes that hearing loss leads to the decreased stimulation of cognitive processing, due to diminishment in speech and language input that negatively affects brain function.
Next one states that people with hearing impairment use greater cognitive resources (attention/working memory/language processing) for listening, making them unavailable for other aspects of higher cognition. This mechanism seems to contradict mechanism 2, however, the critical difference is that mechanism 2 takes place before the onset of dementia, while mechanism 3 makes dementia symptoms worse.
Last proposed mechanism is a hybrid of mechanisms 1 and 3: alteration of cognitive resources as in mechanisms 3, but it interacts with pathologies caused by Alzheimer’s disease, making a neuronal change in the brain.
It is highly probable that more than one mechanisms are possible, however, more research is required in order to clearly distinguish between them for more optimal treatment of dementia in hearing-impaired people.

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