Hearing loss and dementia

I have read a post in the internet telling that some portion of dementia in elderly is caused by hearing loss. Instinctively as well as from own experience, I suspected it could be an association but not a causal relationship.

Actually, the relationship between hearing loss and dementia is one of the topics in the related medical field. Investigating the papers regarding this topic by Pubmed, I found there is no finding that show the causal relationship of hearing loss with dementia. A review has clearly denied it.

I believe hearing function related with dementia must be the linguistic process. Intellectual activity is based on hearing and understanding words/sentences. The hearing by the outer/inner ear, which is often quantitatively measured by audiometry etc, is only perceptive process. In further linguistic process, the information obtained through perception of sound should undergo various processes of morphology, syntax and lexicology, which are handled in the higher center of cerebral cortexes/brain stem. The higher center function is not clearly elucidated yet. Only recently, it has been discussed semiquantitatively by functional MRI findings, I believe. At least, it is still too early to conclude the hearing loss in the elderly causes some dementia. 

I believe this higher center function is more closely related with dementia if it is not a causal relationship. For an example, discriminating a certain speaker among crowd of people speaking at the same time is often becoming difficult for elderly. I suspect this dysfunction of higher center is reflecting the entire dwindling brain function associated aging. Sadly, I am an example of a person with such dysfunction.

Hearing is, however, an important source of intellectual activities. If it is not the cause of dementia, loss of this information source may be indirectly related with lowered intellectual activities.

We should be careful not to lose hearing acuity in this sense. It is not good for us to wear headphone listening to noise for a long time. Repeated fatigue in inner ears may result in permanent sensual hearing loss.