That is sometimes easier said than done, especially when they are unwilling to give up a city and surroundings they love in order to live with or near you, and you are unwilling to uproot yourself and change your life completely in order to go live near them. I've come to the conclusion that older people are not children and that you should not impose your will on them unless they are mentally unable to make decisions for themselves.
Very true, and I have similar issues with a parent myself. However, if they are unable to care for themselves then it is time for an intervention. Been there, done that. Wasn't pretty, but it worked. Look, there comes a time when you become the responsible party. You can't impose, but you can insist. If you have siblings they can help.
A big problem is that people don't always listen to old folks. As a result the most important voice is often yours. It is very difficult to act as an advocate for your parents if they are far away.
If they are in good shape but just need a bit of help there are agencies to provide such services. People who are insured that can do whatever it is your folks might need. Often they are supervised by a nurse or social worker who can stop in on a monthly basis can make certain that everything is all right. SOMEONE should be around monthly or weekly to ensure their well being.
Things have really changed since our folks were our age. The old folks homes now resemble 5 star hotels more than nursing homes. They're bleeding expensive, but well worth it. Many have varying levels of care; from very, very little to a lot. If your folks are having trouble taking care of themselves, such places can be an option, however they are very expensive.
We found out about most of these things from a social worker provided by the hospital during one of my father-in-laws numerous stays. Everyone has had good input, odds are there are agencies where they are that can help you navigate the local health care environment. Often there are no good decisions to be made, and we just do what we can. Good luck.