My dad (84) has dementia. He stayed with me for 7 weeks recently. Why is he now showing behavior he never showed while with me and my family?

Dementia behavior can change drastically, quickly, and then sometimes change back again. Perhaps this is a new stage of the disease. Perhaps his anxiety increased in an unfamiliar place. Perhaps it will ease as he settles in. Perhaps the medication will kick in and be effective. That is a lot of "perhaps", but that is the nature of the disease.

He has never been diagnosed. Do you have any idea whether he is suspected to have ALZ, or vascular dementia, or Lewy Body, or FTD? That doesn't really change anything, but it might (perhaps!) give you a better idea of what to expect as the disease progresses.

If he'd stayed another month with you perhaps this behavior would have shown up at your house. What has his wife been experiencing that led her to place him in a care center? Is the care manager someone at the home?

It is so hard to have a loved one with dementia!

Dementia is so difficult for a family member to deal with. All the erratic behavior, the paranoia, the outbursts...nothing prepares you for handling that emotionally. Parents are supposed to care for children, and when those roles reverse neither party is equipped for the role. Throw in unprovoked, uncharacteristic, erratic and inappropriate behaviors by the one who used to be in charge and you are left unprepared to cope. Dad was good with you for 7 weeks. Treasure that time with him. As his disease progresses things will change...sometimes easier, sometimes much, much harder. Having him cared for by professionals who know when and how to medicate him to reduce his anxiety and paranoia allows you to be his daughter, a much healthier role for you.

katcre, when it comes to memory loss, as jeannegibbs had mentioned above, changes can happen over night. Plus any type of moving of residences can create more confusion.

I think it was great that you took care of your Dad for 7 weeks, to give his wife a much needed break. Apparently she found it more difficult than she could handle so that is the reason why Dad is now in a continuing care home. As one ages, we just don't have the energy that we had just a few years prior. Seniors caring for seniors is physically and mentally exhausting.

I bet even if you brought Dad back with you now to your home, you will find that his memory has failed even more, and that he is now incontinent.

Katcre, all the above. Also, please don't harbor ill-will for your step-mother. She is most likely doing the best she can in circumstances that are not going to be perfect no matter what. And, she's the one your father chose to be his helpmate back when he was in his right mind, right?
Btw, my FIL, 86, thinks his wife is fooling around with one of the employees at his NH. He was the one who always ran around.

Why?

Because he has dementia.

If Dad is 84, how old is the wife. At 65 it was hard for me to care for My Mom. You have to be a special person to care for someone for long periods of time. Was the aide or you going to be at Dads home 24/7. Those with Dementia tend to roam at night. His anxiety can be caused by strange places. You need to allow Dad to adjust. He probably will always say he wants to go home. And it won't be the last place he lived. It could be a childhood home. Are you POA? Without it you cannot make decisions for him. If you don't have it, I am surprised you were allowed to take him out of the facility.

Change is difficult for people living with dementia. Adjusting to new environments can take awhile. Your dad probably adapted pretty well to a visit with you because YOU are familiar and that may have been enough to set him at ease in a place that was not part of his routine. But imagine what he's experienced with his struggling brain – home, then 7 weeks at your house, then home, now a brand new environment that (though it will likely be very much better in the long term) is really confusing and has new faces and routines that he cannot wrap his head around. He'll adjust, the drugs will help in the short term and can probably be cut back or out once he's settled. Give him time and check in a lot to make sure the staff are helping him adjust.

I just recently took him back because he kept saying he wanted to go home and he was asking for his wife all the time. I just spoke to him on Father's Day and he sounded great. His wife did not want me to bring him back at all. I tried to get her to help me with a caregiver, at first she agreed but did not follow through. He was always pleasant at my house except for 2 times when he thought I was his wife and accused me of being out all day drinking and being with someone. He is in a facility since Monday