Elon Musk mentioned the "Elevate the head of your bed by 3"" a few months back. Had an open schedule that day so I said "f-it, let's go look at my lumber out back".

Long story short, I put a 4x4 (3.5" actual) across the head of the box spring and a 2x4" (1.5" actual) across the middle. I have been sleeping a whole lot better even since.