Mental Illness and dementia

I have been asked more than a few times to speak to the prevalance of dementia in the aging person with mental illness. Looking online, I see little to help me. I've connected with a few mental health doctors to help me. Remembering my years of nursing in mental health units I'm not sure how much dementia I saw co-existing with mental illness. I remember at Deaconess Hospital there were people admitted to figure out whether the behaviors were from depression or dementia. Often once the depression cleared with treatment, there was little sign of dementia. I know people with late life depression are more prone to dementia, but I wonder about other disorders people suffer with for years, like bipolar disorder, schizophrenia and personality disorders. If anyone has experience in this field more recently than 10-15 years ago (like mine), let me know. Comment on this posting. I will continue to research this subject