Why you can't sleep... Dream appearances...

I found this interesting thing on Yahoo Answers:

A Japanese legend says that if you can’t sleep at night it’s because you’re awake in someone else’s dream? So I read somewhere today 'that if you can’t sleep at night it’s because you’re awake in someone else’s dream' Do you think it could be true? I think that MAYBE if you're awake in someone elses dream; you can't sleep' but you're not in someone elses dream every time you can't sleep but that's just my opinion I know this might seem stupid to most of you but I was really curious when I read it

Tracking this down, it seems the "if you can’t sleep at night it’s because you’re awake in someone else’s dream" quotation is always stated that way. It doesn't seem to have an obvious source about who said it or what the legend in question is.