I've been thinking along these lines for a long time, especially in relationship to my mother. It really seems her dementia has been progressing linearly with her hearing loss, epecially since she now almost always refuses her hearing aids.

Her blindness (macular degeneration) doesn't help, of course, nor (this is a new biggie) does the extreme isolation imposed by COVID. (Her assisted living facility is one of the only ones in FLorida with no postive cases among patients or staff. This is NOT an accident - they are super strict about following every jot and tittle of the rules.)

This is like a recipe for dementia, though - even auditory hallucinations (which she is also developing).

I remember studying those who "hear voices" and that there is evidence that the auditory cortex is activated when the voices are perceived.

The almost absent socialization from lack of communication created by her deafness already took quite a toll on her pre-COVID. Besides both, she can't even read lips to the degree she had learned to before the bindness became almost total (the masks are the last straw to intelligibility on both sides, of course).

Evidence is strong that even slight hearing loss corresponds with a similar level of cognitive decline, when both are tested. Making a note to make myself wear even uncomfortable hearing aids when the need arises. That is, especially with my sons, so as not to put them through either such decline and the obligatory shouting and repetition my dad's deafness put us through! (I'm glad Medicare has finally passed a rule to cover hearing aids.)

As for my mother, it's as if she were in (a comfortable) solitary confinement - known to worsen mental illness.

Hearing loss and cognitive decline

Yes to all of this, Amanda. Hearing loss contributes to isolation, pandemic contributes to isolation, vision loss contributes to isolation, isolation contributes to dementia.

I worry about my mom-in-law. All of this is going on. We can’t go to see her; we’re many states away. I know she’s safe in assisted living, but it’s not fun being in lockdown. And her skills are slipping noticeably. Facetime/Zoom require assistance. The phone is ok, but I think more stimulus (visual plus auditory) is better, as far as alleviating feelings of isolation.