There is information on this topic on the HLAA website. https://www.hearingloss.org/?s=dementia Studies on this topic indicate there is a connection. Further studies are trying to look at unaided hearing loss vs aided hearing loss through hearing instruments and cochlear implants. Most of the research indicates that isolation and withdrawal are major factors in cognitive decline, whether that is from hearing loss or other issues. We know that people with hearing loss have to concentrate extra hard to participate in spontaneous verbal communication. The fatigue that comes from that often causes the individual to 'tune out'. It's very common for someone who doesn't hear well to appear 'not smart' to others. We respond out of contest, we 'tune out', we don't socialize the way we used to, etc.

Hearing loss is more common with aging, so is cognitive decline. Regardless of the correlation, I believe, very strongly, that it's important for everyone to work hard to keep their brains active by reading, writing, learning new things, playing games, enjoying hobbies, socializing as best we can, and remaining as physically fit as we possibly can.