I think sleep is crucial to health and fitness, just like nutrition. But so is sun exposure, first aid skills, and having a good social life.
We found that if we broadly allowed food and body questions, question quality dropped precipitously and we lost focus. I like first aid (and nutrition, and vitamin D via sun exposure, and socializing); I think everyone should know first aid; I think questions about first aid are valuable; but first aid (like sleep) needs to be out of scope unless it has a specific connection to physical activity. If it's just a general issue of "sleep is good", we need to pass on the question because it makes the site less effective.
There's a separate question about closing the question. Standard practice across Stack Exchange is to close, wait for an edit, then re-open. This seems heavy-handed until you note that the original user (or, y'know, anybody) is free to edit the question to move it in-scope. It's really that answers are verboten when the question is closed. (And the question is slated for deletion after some time.)
I think this was a good use of the close option, particularly since it might drag the OP into describing the reason behind the use of the tag "sports psychology", which might be our connection to in-scope fitness.