Irrespective of the (possible) causative link between hearing loss and dementia, the argument is that hearing loss treated with heating aids reduces the likelihood of dementia.

Anecdotally, I wear hearing aids. I'm always amazed at how much more in contact with the world I feel when wearing them. Without them, all the little background sounds that you perceive are gone. E.g. People chatting. The rustling of your clothes. Birdsong. Running taps. The knocking sound in your car, etc etc. I am totally prepared to believe that the loss of this stimulation increases mental isolation and atrophy.

As a child (with good hearing) I always assumed that I would choose eyesight over hearing if I had to make a choice. Nowadays, it would be a much closer run thing.