What do I do when my husband, who has dementia, stops bathing in defiance?

As you said, your husband has dementia and that means he will require more help.
Which means you will require more help. If you are feeling “defiance” time to get help.
Depending on your insurance, Medicare will provide home health services for him if YOU will allow it. Tell his doctor you can’t take him out easily and he has stopped all hygiene, that you need help with his medication and bathing. They will send out a nurse to evaluate him for services.
So while they set up his pill planner, take and record his vitals, you sit and rest a minute and get to know the staff that will be helping you. They can order PT and OT to help him be more active. They can send out a professional bathing aide who will get him in the shower or tub. If he hadn’t seen a doctor in awhile, that will be necessary to get the services ordered. Ongoing, he can get many of his services provided at home and you can even have Telemed office visits at home.
You see for yourself that he is declining so realize that the decline won’t stop where it is today and if your intention is to keep him home as long as possible, get help now before you are worn out like so many of us are. It may take a few visits but you will see that he will cooperate with others more easily at times than he will with you.
Dont put it off. Call for help today.

Time for your shower. No not now.
You need a shower. No I don't.
You smell stale. I don't.
You haven't showered for 3 days. I showered yesterday.
Please go & take a shower. NO I WILL NOT.

If this is your day, read on. Go make a cuppa. Sit awhile. Sip. Reset.

Such a simple thing, right? Go take a shower...
(except it isn't)

I have my usual routine to shower in the morning. I also can take an additional shower if I reason I need one, after exercise if sweaty, smelly, or after a hot day. I know when my clothes are clean on or not, I can reason when they need washing by the look, feel, smell. Or maybe I spilt something or see a stain.

There can be many factors for shower refusal:
Fear - of falling in the shower.
Pain - when taking clothes off & on, stiff joints, hard to reach, sensitive skin to the feel of water hitting it.
Short Term Memory - can't *feel* when the last wash was.
Sequencing skills: This I feel becomes the biggest barrier. It's kind of a collection of reasoning + processing of information + working memory + planning.

Without: Collecting the appropriate clothes (all the clothes from underwear, pants, shirt), getting to the bathroom, take clothes off now? Or turn the taps on? The water is too hot! Or too cold! I have socks on. Now they are wet & uncomfortable. What do I do with the soap? I'm cold. I don't want to be cold. I don't know which clothes to put on first. I'm still wet. The taps are still on. There is water on the floor. I dropped my clothes. Everything is wet & cold.

Sometimes doing a shower with a person can highlight what's going wrong. Then you can find ways to help the routine, eg
- Have a laundry basket for dirty clothes
- flannel & soap ready in shower
- Have the clean clothes ready on a chair - in order with clean towels on top easy to grab
Maybe you have to stay & prompt each step or maybe just a pop-in visit halfway to wash his back (use a long handle brush).

For some reason, as others have said, employing an Aide to come assist with this task 2-3 times a week gets it done.

My Mother the same. From no no no refusal, denial, resists...
To all smiles when the Aides says Oh look how lovely & clean you are now :)

Have your Doctor get In touch with a social worker who Can help you navigate some services Like a CNA ( Certified Nurses assistant ) for bathing and PT for exercise . Kind of typical behavior - schedules work and routines. For some reason they are afraid of falling and do not Like water . A CNA did wonders for My Dad .

OP, your profile says “My life is no longer my own”. You also say that you “vow to take care of him as long as humanly possible”.

1) Your life IS your own, the only one you will ever have. You have to make the decisions about how you live it. Don’t feel forced, because you aren’t.
2) You can “take care of him” by arranging the care he needs. ‘Taking care’ is about making sure he has what he needs, not arguing about washing with someone who is lazy and argumentative.

Don’t feel that you are stuck in the ‘innocent victim’ role. It achieves nothing, for either of you. Another 25 years of this will kill your love. Find alternatives to preserve it.

I'm guessing that your husband is not being defiant when it comes to him bathing, but instead has either forgotten how or just doesn't feel safe anymore.
Do you have a walk in shower with grab bars, slip proof mat and shower chair for him to sit on to make him feel more secure? If not, I would make sure that you have it all to make things easier for him.(now I understand that not everyone has a walk in shower, but everything else should be had)
My late husband had vascular dementia and I had to help him in the shower(when he was still mobile), and wash him up myself and then help him out and dry him off. Perhaps your husband would let you shower him.
And if not you can hire aides to come in that will give him a bath or shower a couple days a week, as really that is all he needs if he's not going anywhere or doing much.
And you can use the extra large body wipes and waterless shampoo and conditioner caps for the other days if needed. You can order both on either Amazon or Walmart.com.
The fact that vascular dementia is the most aggressive of all the dementias(with a life expectancy of just 5 years)means that your husbands decline will be fast, which I'm sure you've already noticed.
Please just make sure that you're taking care of yourself along this journey as you matter too in this equation.
It's very hard to care for someone you love who now has dementia, but when it's all said and done you will be so glad that you were able to do it.
I was blessed to be able to keep my husband home until his death in 2020, but not everyone can and that's ok too. Everyone has to do what works best for all parties involved.
I wish you the very best as you travel this road with your husband.

Not associated with them in any way but:

Care.com. Many carers have photos with their profiles so he could ( if he still can) have a choice in who he would be interested in working with. There is even a gender preference option to see if any men would be available, if he would be more comfortable with a man.

Good luck whatever you decide to do.

I am having a similar issue. My mom doesn’t change clothes or shower. She becomes argumentative and some times physically nasty. She says she “ will not be controlled And that we want her to die.” We have aides and they also have tried. My parents will not leave their home. This is exhausting. I’m just waiting for her to develop sores/infections.

I haven't dealt with vascular dementia but generally I would talk to his doc about these behaviors and see if there are any meds that could help tone down his negativity a bit?

If you don't have any home caregivers yet, I strongly suggest you do so ASAP. Being the only person for 5 years is just too much for one person to handle. You need a break and some help so you can stay sane and healthy too!

I would also start considering that the time is near (or here) when memory care becomes a good option. Your job is first take care of yourself and second keep him safe. MC would do this.

Best of luck.

Ignore him and go about your day..........expending huge amounts of energy on a defiant person just sucks the life out of you. Hire a male Visiting Angel and see if he backs down a bit. Last resort, call Adult Protective Services to evaluate for placement.

I'm able to put my mother into the shower weekly in spite of her resistance. I'm running a dictatorship, not a democracy.

However, if I had a man who most likely would be bigger and stronger - not to mention I have absolutely no interest in bathing a man - I would hire a male aide to come in and do the showering.