Thoughts on lying to a parent suffering from dementia?

ABSOLUTELY.
I was raised, or developed my own moral/ethical compass and I wouldn't lie either...but this, you will discover as time passes, is a game of survival...for ALL. Your dad is right...It truly is okay...otherwise it increases upset and that's not good for any of you. You might start to develop a knack for it. Sort of a diversion/distraction game. The last trip my parents took a few years back to visit my sister was when we got slapped in the face with what was going on. Sister is out of state. Plane trip went fine...but on arrival we discovered how she had barely packed...and she began to whine about wanting to go home. When told the truth (going home in 9 days) she went into auto mode about oh no, she had bills to pay etc. Finally my sister just by chance said "the day after tomorrow". And that shut her up and worked...it had to of course be repeated, multiple times for the next 8 days...but it worked to appease her. If you had a good relationship prior, she will no doubt continue to trust you. Good luck...

It is absolutely ok. It will give her peace. She can't control the irrational thoughts and you just need to acknowledge her.
If she is like my mother, she won't even remember the conversation the next day and it will all be behind you. but at the time, you were able to give her peace when she was experiencing fear.

She most likely won't remember what she asked you or what you told her. I used to tell my Mom happy stories, mostly made up. Whatever made her feel ok. And I think that was the right thing to do.

Most of us are, or at least were, like you... We want to be truthful, but when the truth hurts rather than helps, we need to find a way to avoid that. Bending the truth, fibbing, whatever we want to call it, it is done to calm the person, to assuage their concerns and anxieties. REAL lies are said to hurt others, CYA, get some gain for oneself - they are hurtful and wrong. The fibs we have to use are not done to be hurtful. What becomes hurtful, over and over, is telling someone the truth about those who are no longer with us, as they won't remember and have to hear and suffer from "the truth" every time, often multiple times a day. It also, as you have found, applies when they no longer recognize us. I haven't been able to visit my mother since 3/16, so it will be interesting to see if she remembers me. She did every time I was there, likely because she's living in her reality from about 40 years ago, so I was already an adult - not too much different, yet... She used to periodically ask about my brothers, but they really haven't been visiting (OB hasn't been around in over 2 years, YB doesn't really visit, but is needed to take her to one appt 4x/year for eye treatments (I did this for years, but can't support her weight now and she won't stand/walk without a lot of help), so she gets a little memory jog when he has to do this (and has tried the last 2 times to get out of it!) She did stop asking about them - I chalk that up to out of sight, out of mind. Without periodic "reminders", the progression will eventually wipe us out of any more recent memory... Probably a lot to be said for socialization helping to slow the progression...

I would not worry about these little confabulations setting up any kind of distrust from your mother. Her reality is now many years ago, and her denial that your dad is her husband is likely mired in that - he does not look like the man in her mind/memories. Your dad must have learned about this somewhere and it is good that he is okay with it. It's sad that she doesn't acknowledge him now, but if he wants some comfort from her, perhaps he could get some by phone - she might recognize his voice but not his current image. During one of those "errands", he could call when not in her sight and say he heard she was worried about him. He could chat for a few minutes, perhaps making both of them happy for a little while, and then say he'll be along soon, he has to finish work or errands or whatever excuse comes to mind. Because she won't remember your fibs for long, they shouldn't cause any distrust to set in.

Always keep the "return" vague, as you did (be right back, soon, in a while, etc.) Their concept of day/time is also out of whack, so try not to use dates or times. Just soon, later, etc. Be there for your dad. This is very hard on him!

When they have dementia they are in their own world. It is perfectly fine to talk to them about their own world. Go along with whatever they are talking about. Say whatever to calm them down at the moment. If the truth hurts, don’t say it. They are going to forget anyway. My brother did this with his father n law who had dementia.

Excuse me if I say something that others have said (I have not read the answers yet), but your question rang a bell with me. When I expressed this concern to my in-laws' physician, he said that it is sometimes necessary and we need to think of it as "therapeutic lying." It doesn't help - and can actually hurt - to tell people with dementia "the truth" in every circumstance. They can't necessarily accept the truth and sometimes it is just easier to go along with them or to squelch their fears by telling them something that isn't true so they can be calmer and have less anxiety.
An example that we recently experienced was having to decide to take my father-in-law off dialysis. He had Alzheimer's and it would have done him NO GOOD to tell him this. He was still cognitive enough to wonder why he wasn't going to dialysis, so we were told to tell him that he wasn't tolerating dialysis very well (true) and so he was having a break. He wouldn't have been able to understand at this point that he was going to die. It was difficult (as this was during the beginning of COVID and we couldn't be with him in the nursing home) but he died very peacefully.
Sadly, we have to be quite sneaky with Alzheimer's parents sometimes. It is hard on us! But try to think about things ahead of time and plan for what you will say, etc. We also learned that it is best to say TOO LITTLE about something rather than TOO MUCH. Blessings to you.

My mother occasionally asks where "dad" is. He died in 2018. He was often out of the house doing yard work, so we tell her, "he's around," "I think he's in the yard," etc. But sometimes she asks if he's dead. I then tell her he's passed away. She was with him when that happened, attended the funeral, etc. But does not remember any of it. When she hears he's gone, she gets a little teary. But within 30 seconds, she asks where dad is-again, and again every minute or so. So she cannot retain recent memories at all. We then tell her "oh he's around..." and that is all the longer she remembers. When this goes on too long, best tactic is to distract with some other topic of conversation that interests them. Or "how about a cookie? How about a soda?" That works,

Once when she was persistent in asking, she was told dad passed. She then asked "where is he?" He was cremated and the urn is in our church mausoleum. My brother told her, "He's at the mausoleum, lying right above (name of a neighbor who passed.)" She got a laugh out of that! So there's no telling how some of this stuff registers in a damaged brain.

Don’t think of it as lies, think of it as ‘telling a story’. We read stories all the time, and don’t think of them as lies. Often in our own mind, we enter into the story world. Think of this as going into the story world of the person you love.

Imho, sometimes a "little white FIB" must be employed.

don't feel bad about telling a little white lie, when dementia enters the mind, it transforms them into something else, you just have to play along. Tell her, like your father said, that her husband was doing errands and this man is just there to keep her company until her hubby gets home.  It eases the "dementia" mind.........later she won't remember what she was worried about.  its like intermittent amnesia takes over and then her mind comes back.  It happens to most everyone with dementia at some point.  Sometimes my father would think his wife of 75 years was his mother and then the next time it was his wife.  And I even became my fathers, wife, and then his daughter.  this disease is complicated and confusing to those of us that don't have these issues.  I wish you luck, but do what will keep your mother from getting upset, so the white lie isn't hurting anyone.

She has dementia so appease her with white lies. If it calms her down do it. She won't remember. You are NOT lying, you are calming her down.

A very wise Hospice social worker told me that they are called ‘loving lies’ I took care of both my mom and dad who both had Alzheimer’s and honestly that is the only way I got through it! I used to joke to my friends that I lied to my parents more now than when I was a teenager !! Humor gets you through it sometimes!!

Think of it as you are getting into her world. With this disease one has to in order to keep them calm.

The most important thing is to provide them comfort and relief.

if you told her the truth, it might intensify her confusion and fear.

Make sure your Dad has breaks - maybe you can hire someone and spend some focused time with him. This is so painful for him.

Although my wife 60 YY is only in earlier stages of dementia there are some things that she cannot remember ever talking about. Her dog Cinnamon died,( Cinnamon was 18+ years although we only had her for about 6 years). My wife asked about Cinnamon as she knew her health was poor. When I told her she had died she went through about 4 days of crying.
About a week later she again asked about Cinnamon, I told her she died the past week. Another 4 to 5 days of mourning. After that whenever she asked about her dog, "everything is fine" until she completely forgot about the dog.

It is called "Therapeutic Lying."