Which end is raised? The head end?

That would make some sense for me. I'm one of the many, many people who's llower esophageal sphincter doesn't close tight enough, allowing stomach acid to trickle up into my throat, causing inflammation.

Would not the perfect position be more hammock like, ie sagging in the middle so that everything naturally drains towards your bum, where the necessary biology is in place to deal with toxins? Otherwise would you not be increasing the risk of thrombosis in your lower legs, due to the blood welling up under gravity, with the reduced heart rate and activity of sleep?