I am Mom's Power of Attorney - do I have to call all four of my siblings on health updates on my Mom?

Does she want you to? It's her personal health information. As power of attorney, you are acting on her behalf, as she would do if she could.

As her children, they are surely interested in how she's doing. Personally I would not make four separate phone calls. If you decide to send updates, do whatever is easiest for you. There are sites like CaringBridge that everyone can use to stay up to date, or you can just send out an email.

No, not necessarily. It should be as your mum would or does want.

When my mother first was being tested and diagnosed with dementia, she did not want anyone to know, nor to see her, Once she was placed in a facility I forwarded the address and her phone number to family and friends and she welcomed visitors, As regards her health, I only informed my sister of any major changes. Can your sibs can visit and talk with your mum about her health?

You are busy with your mother's care. Personally, I don't think a blow by blow account is necessary. A periodic email to everyone you wish to inform should be enough unless there is a health crisis, or, as Jennifer mentions, a site like CaringBridge.

Be sure to take care of yourself. This is a difficult journey.

When you do want to give updates, choose one, tell that sibling, and that one can pass it on to all the others.

Or, you can wait for those interested enough to call you.