Age won’t be a problem if that person needs to be put in a nursing home, my friend’s uncle had a car accident which made him unable to take care of himself, he was 34 yo at that time, he still in the nursing home he’s now about 55-57 yo.
There are some nursing homes that do have age requirements.. I live in Jacksonville FL and I have been checking out several for the future.. my husband is 63 and declining with his LBD and Parkinson's. I know I won't be able to care for him in the future.. I have checked out all the top rated homes in town and 2 of the have a minimum age of 68. the average age is 85 I was told at both of them.. So, you need to inquire with each NH you are interested in to see if they have a minimum age.
There is no age, as far as I understand it. It is based on "need" or inability to care for oneself. There are 'young' people in nursing homes that have brain trauma, etc. It is based on the inability to care for yourself.