How much should I help with my sister as she slips from mild cognitive decline into severe decline?

"Her husband is good with her, but he's got a ton of work/aging parents/church leadership commitments and can't be there (physically and mentally) all the time."

Tread very carefully here. Does bil work long hours? How much does he do for his aging parents? What are his church leadership commitments?

You need to remain a supportive and loving sister, NOT the caregiver. Are you retired? Beware of mission creep.

First I will say that your sister is not your responsibility, but her husbands. It will be up to him when the time comes, to set up in home care and whatever else she will need. You need to just be her friend and her sister, and just continue to be there for her, without trying to "do" things for her. Let her do for herself as long as she is able, as it will hurt her more than it will help her if you try and do it all for her.
She's still your sister, and even though she's showing some signs of mental decline, please don't patronize her, and make her feel worse than she may already be feeling about it all.
And if she struggles to find the right word, oh well. And if she laughs about it, you laugh right along with her. Don't make it a bigger deal than it is.
You'll figure things out. Again, just let her know that you are there for her, and that you love her.
And it probably wouldn't hurt for you to start educating yourself about dementia. Teepa Snow has some excellent videos on YouTube, which would be a great place to start. I'm wishing you and your sister the best.

Sounds like sister’s husband is playing ostrich. He’s avoiding the situation at home by getting away from it as often as possible. While she is his responsibility, she is still your sister and you are concerned about her. Have a talk with him and offer to help so he knows he isn’t alone in dealing with this. He’s probably afraid of what’s happening and at the same time he doesn’t want to acknowledge it. Your sister should have a neurological exam as there are medication that may help her.

"...your sister is not your responsibility, but her husbands." Absolutely agree with funkygrandma59 on this.

As an elder in a church we helped plant, I can tell you that her husband will need to ask others to cover his responsibilities so he can care for his wife, just like he would hope she would have done for him. If he doesn't get coverage, oh well, the Lord will figure it out.

By all means watch the Teepa Snow videos (maybe do this with your BIL) and be helpful to him, but don't enable him to be uninvolved.

Her husband's first responsibility is his wife. Are his elderly parents still living on their own because he helps. May be time to look for a place for them where they get the care they need. He needs to start backing out of his Church committments unless he is the minister, then maybe he can get help with his work load. He may want to start thinking of retirement. If he is also 65, he can retire at 66+4 months to get 100% of his SS, same with your sister.

Its nice for you to "be there" but he should not lose sight that his vows say "in sickness and in health" and as a Christain man he needs to honor them. We had a lovely man in the Church whose wife had water on the brain which causes Dementia type symptoms. He cared for her 24/7. But he loved working in the Church. (She did too) When his expertise was needed, the Church women would get together and take turns watching his wife for him. When he had to place her, he was there every day. He had lunch with her and then stayed the afternoon.

So, do not allow this man to rely on you too much. He too will have to eventually place your sister. Caring for those with a Dementia becomes 24/7 care. You can offer to grocery shop, maybe sit with her while he goes to a meeting at Church but her primary care is his responsibility. You have your own life too.

I am sorry about your sister's dx. Your sister is indeed most lucky to have you alongside her.

Your B.I.L is an active man. I get that - he needs to keep living too.

I suppose continue to talk to him about your sister. What you can do, what other caregivers he may need to add in as time goes on as more supervision is needed (ie paid aides).

If he is VERY busy, being the good son carer, the good churcher, the good worker, but also the good husband, well ok. But if hiding out in his activities, he may be overwhelmed or in denial. There will be grief too.

Sounds like you are finding out how to connect to your changing sister very well. Just keep following your head, heart & gut instinct & you'll do fine.

Your sister is probably very aware that she is "slipping" and wants to retain some semblance of control over her life - don't we all? Ask your BIL and sister what areas they would like you to help with: cleaning house, laundry, taking sis out to shop for groceries or for her appointments (medical, hair, nails)... Then, proceed with the areas that they agree where you may help - with a kind, gentle and probably humorous reminder that it is time for you to play "house elf" or "cleaning lady" or whatever tickles your sister's funny bone. As you notice other areas that may need some help, gently suggest adding these to your "to do list". Just make sure that you do not become so overburdened that you neglect your own home, health, and other relationships.

As for conversation, it requires patience to "wait" while your sister searches her mind for the word she wants to use. If it doesn't come or she laughs it off, just move along in the conversation as if she "filled in the blank." If it is vital information, write down a question about the topic that her husband can fill you in on later.

You say, "I don't want to jump in if in any way it marginalizes her." She's already been marginalized by dementia, so, YES get in there an help, both her and her husband.
a. regarding forgetting words: with practice you will find the best way to help her. Let her search a bit, then fill in the word she is looking for. You don't need to get frustrated, one frustrated sister is enough.
b. she may not be the same as before but as you say, "we've always had a great relationship and I want to be there for her". You just answered your own question. Don't take over, start by just being her sister. Visit often, she really needs you more than you know.

If it were me and I considered myself a loving sister (even though your BIL is not helping out as much as he should, in my experience most men aren't great at caregiving) I would help as much as I could especially that both of you live so close to each other.

I suggest you watch Teepa Snow video's on youtube. Those video's helped me to learn how to deal with my Mom who has dementia.

I wish you and your sister the best!
Jenna

One of the things we all cherish is our independence. Allow your sis to do as much as she can by herself without being unsafe. It's nice you are helping her but don't tell her “she can't”. You might offer to give her a hand when she's struggling, or do what you want, like clean out the cabinets, when she's not around.

It can be maddening trying to communicate with some who is always searching for the right word to use. Don't make a big deal of it. I'm sure it's embarrassing for her and frustrating also. Give her time to come up with the right word, then offer what you think she might mean in a pleasant way. As for you, speak slowly, be in front of her, and use simple sentences. I like your approach of smiling when you interject.

When it gets difficult for you, make it known to her husband that he needs to reduce his commitments.