How do you know if a parent needs to be evaluated? How can I encourage him or his doctor to work on that?

According to a DNA test, my father and I have a slightly increased genetic risk for Alzheimer's. Interestingly, that was not reported for any of my other siblings, or for my mother, although some of her relatives did have symptoms. I live with my parents and a sibling who has trisomy 21, which is also a risk factor for Alzheimer's. My father's mother had dementia, but we know some of hers was due to strokes. His father had cardiovascular problems, but seemed mentally sharp right to the end.

Dad is over 80 years old now. That probably puts him in about the right age range for late onset Alzheimer's. Mom and I wonder if he is showing signs of slight decline, but he has always been quirky and "absent minded". We think he is "on the (autism) spectrum", but he was never formally diagnosed or tested for that, as far as I know. Two of my sibblings were diagnosed as adults. It can be difficult to know when to take things seriously, because Dad likes to joke about things in a way that makes it hard to tell if he really means what he says. I would love to have a neurologist do a thorough exam so that we have a better idea of what we are dealing with. I don't know if I can suggest that to his doctor. I don't know what would happen if I did suggest it. When I mention it to Dad, he typically dismisses the idea with one of his not so funny jokes. Mom and I can discuss these issues with him in the room, and he usually doesn't even notice because he's so absorbed in something on his computer and/or has headphones on, and/or he is asleep and/or just not paying attention. When he does notice, he usually asks questions as if he doesn't understand, or the idea is new to him, or doesn't particularly concern him. It's possible that he feels threatened or apprehensive and wants to avoid such topics. He is by far the most independent person in the immediate household, and I'm sure he doesn't want to us to take away his independence, but how do we know when it is time to have a serious talk, or what the first or next step should be? Who do we talk to? How do we get him to take it seriously? How do we know if a little thing he said or did was something to worry about or not?

If he walks in the middle of the street or crosses at inappropriate places, is he being careless because he knows he's in a small town and doesn't expect much traffic, or because he has forgotten about safety, or never learned basic road safety in the first place? If someone else did the same thing and got hurt, he would blame them for being reckless. If he hasn't been seriously hurt, do we just assume he's fine and let it go? He tripped on the sidewalk while walking al over town alone one evening. After he walked home and got bandaged a little, he realized he didn't know where is cell phone was. Judging by the way his hands and face were scraped, he might have been looking at the phone when he fell, but maybe he dropped and forgot the phone because of the fall. We went looking for his phone and I called it to see if it would ring. Someone had found it and they brought it to us. Then we took dad to urgent care. I waited with him, and wanted to go in with him to talk to the doctor, but when I asked, nobody wanted me to.

Dad doesn't drive a lot if Mom can do it, but he does drive. He would rather read if he can, and i think he would not deny that Mom is better at driving. Once he was driving to a restaurant we had been to before, and he turned onto the wrong side of a divided road. My sister and I both told him he was going the wrong way before he turned into a parking lot to turn around. I don't remember seeing oncoming traffic, but when I tried to point out the spot where it happened later, it always seemed like there was traffic. Nobody got hurt, and people do make mistakes sometimes even without dementia. So, how do we know when to take his keys away? He had laser surgery a couple years ago and can see better than he could for a long time. Maybe his vision was part of the problem, but I don't think it was all of it.

He leaves doors open or unlocked. He leaves toilets unflushed. He needs to be reminded to wash after coming in the house or picking his nose. He has been scratching his crotch in front of people more than he used to, and a couple years ago he started walking around the house nakedness, but I think he stopped that after Mom had a talk with him and he bought himself a bathrobe. I don't think he knew that sometimes I would just look away or hold a book or iPad up to block the view when he came walking nonchalantly into the living room with nothing on, as if it was something he always did.

He asked me 2 days in a row if I had ever used DuoLingo, or if it was on any of my devices. I had been using it nearly every day for months. I had shown him the app on my phone or iPad multiple times. Many nights Mom would read reminders from DuoLingo when she found them on the ipad. I don't know how many times I had discussed it openly when he was around. Sometimes I showed him parts of my lessons that I thought he would find interesting, and he didn't understand what I was showing him or why other times took my phone from me and read every word on the screen, trying to figure it out. Sometimes he did understand that it was a language lesson and he spent more time than I expected analyzing and ecpounding on what he saw or what it reminded him of.

Once he got excited and took off his headphones and turned his computer around and played a silly and annoying song that he had sung many times over the years, probably before I was born, but he especially liked singing it to kids. He asked me if I had ever heard the song before. I said "many times." He had acted like it was sime great new thing he had just discovered and wanted us all to stop what we were doing so he could share it.

He interrupts a lot. I can be mid sentence and he just talks right over me without making any attempt to listen first and see if someone was already talking. He can be looking at something on his computer and suddenly start yelling or lecturing about it as if he thought people in the room needed to hear his arguments or had caused the situation (usually political), when we have been calmly doing things that have nothing to do with the doomscrolling on his laptop.

Last night we went to a play (Matilda, the Musical). It was his idea to see the play. I had considered auditioning for the play, but it's a musical, and I am not a confident singer. I lost track of when the auditions were, but I had watched the musical online multiple times since first hearing some of the songs on one of the music stations Mom turns on at night, years ago. I thought we had all watched the whole musical on TV at least twice. After the show, Dad commented that he was surprised it was a musical version and asked if I had ever seen it. I just said "Yes.". There have been other times when he has forgotten that he ever saw movies or TV shows that I was sure he had seen. I guess most of us do that sometimes, but it surprises me sometimes the things he either forgets or never noticed. Sometimes it's an episode of a show that he bi ge watched after midnight years ago and invited me to watch with him. He liked it so much he bought the entire series on DVD. I happened to find a Facebook group that watched an episode of the show at a time every week. I don't know how many times we had watched the entire series, but every once while, Dad would say "Have we seen this one.", or "I don't think I've ever seen this one.", or he might ask questions as if he had no idea what was happening.

He will jump in at the end of a show or a conversation and ask a question that only demonstrates that he hasn't noticed anything about it until the conversation or show was basically over. He might ask a question and expect me to answer right as the show is coming to its conclusion, so that if i aswer, i will miss the conclusion. Sometimes we have to rewind to the beginning watch again. If we do, he might just fall asleep.or get back on his computer anyway. Mom gets frustrated because she wasn't talking to him anyway, and if he doesn't know anything about it, she doesn't want to start over and explain everything to him. He gets mad because of her reaction and says he just wants to express an interest in what we're tslking about, or that he's concerned about a person or situation he really doesn't need to know about. (For example, maybe a child Mom and i have both taught, but who he has never met.)
Sometimes if we try to answer, he loses interest and wanders off anyway.

How do I know when Dad is just being who he is, and when he is charging? How do I know when to ignore little things, and when maybe it isn't a little thing? How do I know if there is something I can or should do to help? How do I know when I need someone else to help?

He was never a caretaker, and I don't want to be his caretaker. Mom is the main caretaker for my little sister. I stayed with them partly so Mom wouldn't need to do that alone. We have had my little sister for almost 40 years now. Her first language is sign language, and I think Dad knows less about communicating with her than the sibblings who don't live with us, and even some other relatives and friends.

I see things about walking for Alzheimer's and maybe there is a local support group I could get involved with. I have talked to people about it at community health fairs, but I don't know if I can commit to being on a committee or even doing a walk. Dad loves to walk. Maybe I can get him to walk with them if I go with him. He still walks much faster than I do, and goes all over town and across the bridge to the next town just for fun. We usually don't know where he goes. I can't do that because someone has to stay with my sister, and I have been struggling with spinal stenosis especially since covid. Mom had a hip replacement a few months ago and might need another eventually, so she doesn't walk as much as she used to. My brother and his wife run in races often, but they are busy with their jobs and kids.