Challenges of Learning Language in Old Age

I have recently heard from two elderly people how they feel as though it would be more difficult to learn a language in their old age then if they had been younger.  I was wondering about this what some of your eperiences are.  Do you find that it is more diffuclt because it is harder to remember things or do you find that it keeps your mind active and helps you to remember things?  I hope I do not offend anyone with this, but I am very curious as to what the case is