My Mom's (82) conversations always go back to the past. Is this normal?

My dad , with dementia, has very little short memory. He has amazing memories from 25 to 60 years ago. I have been taking advantage of his old memories in two ways. First, it's facinating to learn more about my family history, dad loves to reminence, and second, it's a great way to distract him from being stubborn about something in the here and now that he can't understand or remember.

I think as dementia progresses, it's easier to replay the old "stories" that you're already familiar with, than to interpret and understand whatever is going on currently. When you think of everything that goes on in your head as you're being told a story, or experiencing some sequence of events, it's very complex:
Understanding the time frame
Is it someone's personal story, or is it being told in the 3rd person
Is a conversation being related, is a joke being told, did some action take place (like slipping on a banana peel, for instance)
Are others contributing to the story
My own head's getting tired just thinking about it. :)
When I've had a really long day and just want to unwind, I don't feel like watching a new movie, or picking up a challenging book, or meeting a bunch of new people. I just want to watch a familiar sitcom on t.v., or read something by my favorite author whose style I know really well.

I started to notice about 4 years ago my Dad started talking about the passed more and more. He would go back in time usually when he was in his early twenties. Before this, he never really talked about this time frame in his life too much.

Then this focusing on the passed started to coincide with more and more memory issues. It is very difficult for him to carry on a conversation about events that happen in the present.. unless it is something that just happened that day.

So for my Dad.. it was a beginning of the dementia. I think his memories in the passed are the strongest as the most recent ones are easier lost.

Unless the elders are around people of their own generation, such as living in Assistant Living, they tend to revert back to the past as that is all they are familiar with. My Dad does that on a daily basis because he and Mom still live in a subdivision where there aren't anyone their own age group.

We probably would do the same thing if we were around only people who were 30 to 50 years younger then ourselves. I can relate to Frankie Valli & The Four Seasons but cannot relate to Marley Cyrus. I can relate to Doris Day and Rock Hudson but could not identify in a lineup any of the much younger actors.

By memory, I mean short-term memory like what day it is, what they ate for lunch, if they went to church, etc.

Not necessarily. Old people tend to live in the past. Unless it is coupled with a noticeable loss of memory and reasoning, I wouldn't worry about Alzheimer's.