That’s a great question! Let’s ask a slightly different question first – “do you sleep more when you’re growing?”. The answer to that is yes! When you grow, you’re using quite a lot of energy, so you sleep to conserve what energy you have in order that it can be used for growth.
So if you’re asleep, then energy that you might normally be using to run around everywhere can be used to help you grow. So while I don’t know the answer for sure, it seems sensible to suggest that you might grow quicker when you’re asleep!
I agree with Pete – it seems logical to think that you would grow slightly quicker in your sleep than you would during the day! Gravity may also have something to do with it….when you’re awake and standing upright, gravity pushes your feet to the ground to stop you flying into outer space!! In essence, this acts from your head through to your feet…when you’re lying down asleep though, gravity is pushing against a larger, horizontal surface area of your body. What do you reckon Pete? So it would make sense to think that a combination of the energy and gravity viewpoints would make you grow slightly faster during your sleep!