Hearing Loss Can Can Accelerate Brain Volume Loss
Well, when it comes to hearing loss, that seems to apply to not just hearing per se, but the actual structure of the brain!
Researchers studied MRI scans of older individuals (ages 60-77) with hearing loss, they found less brain volume in the auditory cortex of the brain which is not entirely surprising. What was surprising was that there was less brain activity on functional MRI scans when these individuals listened to complex sentences (it is just not "hearing" that is lost, but higher level brain function of "comprehension" being lost too).
These results suggest that hearing loss can lead to a systematic decrease in neural activity of speech comprehension and may also contribute to loss of brain volume especially in the primary auditory cortex.
This finding also implies that by wearing hearing aids, such loss can be prevented.
The next step would be to do the same research on patients WITH known hearing loss, but hearing aids have been used. What would be also interesting would be to see if such brain changes can be reversed if hearing aids are used after such brain loss is seen on MRI.
Hearing Loss in Older Adults Affects Neural Systems Supporting Speech Comprehension. The Journal of Neuroscience, 31 August 2011, 31(35): 12638-12643; doi: 10.1523/JNEUROSCI.2559-11.2011