Will schizophrenic people develop dementia and at what age

Not typically: 1) There are several types of dementia, so it is hard to generalize. 2) Neither schizophrenia nor Alzheimer's (a common dementia) are well understood as to mechanism and are quite different. 3) Predicting who will get dementia is the subject of research, with little clinical evidence. 4) A single patient can get an MRI or PET scan, but even these tests confirm or exclude and do not predict well.