Yes, it's pretty well documented now as well. Lack of sleep in particular causes a lot more health issues than people are aware of. For example heart attacks increase by about 25% during the spring loss of just one hour's sleep for daylight savings. Muscle and joint health are part of a long list that can be affected by lack of sleep.
There is a reason why pros in modern football are warned off partying, drinking, being out late etc, in excess. To what level Neymar is doing it I've no idea. The other thing is a professional attitude, because you can do it in down time but Juve are famously strict with these things. Dani Alves moaned because he couldn't play his shit music and dance around, ffs.
This is what he said recently.
So yes, while his stats might be good or very good, we really don't know for sure how detrimental his behaviour is to his fitness or stats. He might have fantastic stats instead, he might have less injuries, but it seems clear that he isn't going to change his ways. Lolzilian...