I didn't find cites that says born deafness contributes to dementia. I found claims that says isolation, due to deafness can contribute to dementia, in other words, it's not the deafness it self, but problems with coping with it. Feel free to correct me.Not true. Isolation caused by deafness whether born or acquired were both seen as contributing.
In other words, it's bad if you are hearing, and start to loose hearing at an age of 50 to 70.
That's why I say it's safer to be deaf from early on than hearing.
Mind you, I am taking an ethnocentric deaf perspective here. One can perhaps find flaws, but it's comfy..