If you want to avoid back problems with a mattress, sleep on your back and put pillows under your knees. That causes your spine to be straight, and voila, no more pressure points.
(If you're vain it is worth noting that if you sleep on part of your face, every night for your life, you will get wrinkles there much faster. Therefore sleeping on your back will keep you looking better, longer.)
Some of us simply can't sleep on our backs. When I try, I end up feeling and hearing my heart thumping loudly in my ears and have to roll over onto my right side.
(If you're vain it is worth noting that if you sleep on part of your face, every night for your life, you will get wrinkles there much faster. Therefore sleeping on your back will keep you looking better, longer.)