Well, going the other way there is (I never said it was high quality, but it Is fun) Margaret Ball's Mathmagic- about a woman who grew up in what we see as fantasy land and comes to our world for a better future for her child- and then has to go back to rescue said child through a series of complications. It seemed vaguely relevant.

There is a set of books, I'm forgetting the author and titles sadly (but they used to be on the bottom shelf of the paperback SF/F books at the Hamden Library) about a vetrinarian who is brought into a fantasy world for her medical skills just as she's contemplating suicide because she might well have huntington's chorea. Definitely an adult, although far from middle aged.