Am hearing this for the first time but am pretty sure it depends on which position you sleep with when having your phone. Have been sleeping with for phone for quite some years now. But then, I somehow second you in this. This is because, most of the times especially when am at home, I usually put my phone under the pillow so there there's no direct contact with my body and the phone. But lately, since am.in school and the theft rate is pretty high, I prefer sleeping with my phone besides me. And there's this day, I work up and found it very hot but I assumed maybe its because of my body warmth. At least now I know the effects of sleeping with a phone. If I must sleep with it then it should be under the pillow as I used to do before so that my body isn't attached to the phone.