Like Christine said, AD (Alzheimer's) is a type of dementia. Vascular dementia is another type of dementia. Dementia itself is just a collective term when you don't have specific diagnosis (e.g., Alzheimer's, or Vascular dementia or others.) At times people don't have specific diagnosis due to lack of opportunity to diagnose it without any objection by the patient himsef/herself, so they call it dementia.

My mother always thought vascular dementia is Alzheimers because she may have vascular dementia in the future if she has more minor-stroke. But the cause is completely different. If you search the website for dementia, you will have more info. on that. There are at least 7 types of dementia!!

About being combative: they are combative because they are in the later stage of the dementia. Esp. Alzheimers, for stage 6, the patient, like my father-in-law, is very confused and is losing reasoning and logic. He or she cannot understand the reason for some social behaviors or conversations, he would get violent or use force. e.g., if the caregiver tries to tell my FIL not to play with the remote control or the phone not wanting him to damaging it, he would use his force if he feels that someone is taking something away from him without reason or without the right reason in his own mind. That is, he would resist anything that is against him even if it is reasonable in normal people's mind. Early Alzheimer's does not have such behavior as he knew that he should not hit people. Now he is at the point that he has no idea why he cannot hit women who are the caregivers. So we just try to let him do what he wants unless it is very dirty or unreasonable. If he wants to play with the phone, let him; if he wants to touch the bowel in toilet, they would throw it out and told him to wash his hands. This way he would not hit people or use force as he told me he would.

Regards,

Nina