Able to manage personal care with some help
When it happens
At any point in dementia. Many people begin to need increasing amounts of help from the late mild stage onward. (Others, who have other health conditions, may need a lot of assistance from the start.)
Why it happens
Cognitive changes begin to make it harder to remember to do basic self-care tasks (or how to do them). Eventually it may also become harder to identify and know how to properly use the necessary tools involved (toothbrush, shoelaces, shower). As the brain and body have more difficulty communicating, there's a growing difficulty in coordinating the multiple steps that a healthy person takes for granted to do something like walk confidently, insert an arm into an armhole, or sit down backward into a chair.
What you can do
Err on the side of doing less, rather than more, at first, to promote independence as long as you feasibly can.
Know when to "butt in": Help when it's asked for; when the person is beginning to show signs of frustration; when health or safety are at risk (such as not bathing).
Allow more time for basic tasks; try not to show impatience or irritation.
Be respectful when you have to get involved. Instead of, "Here, let me do it," say something like, "Those tiny top buttons are tricky; may I try?"
Respect privacy involved in tasks like bathing and toileting -- they must be done, and by definition helping someone do them makes the activity not "private," but by staying matter of fact and discreet you can eliminate some of the mutual embarrassment.
Use humor to defuse awkward situations; you may both find it a relief.
Bring in additional help to share the physical burden. Consider night care, or someone to do tasks you're most uncomfortable with or that the person with dementia is uncomfortable with you performing (for example, a man might be more comfortable being bathed by an aide or a son than by a daughter).
Research care alternatives for the future, in case a move is necessary. You're not committing to a plan, just researching options.