How common is it for people with dementia 2 have hearing loss? What causes this?

Usually unrelated. Dementia by itself does not cause hearing loss. However, hearing loss can lead to some symptoms that are similar to dementia caused symtoms.
Not common. Hearing loss is common in the same group of age but is not caused by the dementia unless the pt had encephalitis. It is likely a coindicende with sensorineural herring loss.

Related Questions

Anyone have any experience with sudden hearing loss and dementia? Are they related?

No experience. Any sudden change like that would be an emergency, such as a stroke or infection of the brain inner ear. Since dementia is just a general term which could include multi-infarct dementia due to multple strokes, one of them could affect the hearing areas. Also if the person lost speech, which is common in a stroke, you might not easily know if they lost hearing or just the ability to respond. Read more...