It was time to replace my old mattress so I bought a memory foam mattress. I was a normal healthy person... then my back started to hurt then got worse. Went to the Dr.  He did x-rays. I had a curvature to my spine and the curve to the small of my back has flattened. Every step I take shoves into the nerve running down my leg and it is more painful than you can imagine. I understand memory foam. It is fast and cheap and they can put it in a box and mail it to you. Easy peezy... profitable. Soon it won't be so cheap and neither will your medical bills.  I regret the day I ever bought my memory foam mattress. . Wish I could buy a time machine.