Not sure, but as a child I slept A LOT. The result is that I am now over 6ft tall. Oddly enough my mother and father are adverage height of around 5'7". Good luck on your quest for a solid answer. I would propose that you apply for a government grant and offer to do a case study on the subject.
There sure is, the pituitary gland releases growth hormone while we sleep; one of the reasons that children need a lot of sleep. I haven't studied all the stats, but I'd venture a guess that if you did a study of the most developed (muscle mass, bone length, height, etc) of children; you'd find that these are the children who by and large, got the most sleep. Annie