For those who wet the bed or wears diapers and sometimes wet through you might think about getting waterproof sheets. I found some (twin bed) with elastic corners for $4.57 at walmart but i would put the extra 2 dollars forward and buy the one that has a zipper and covers the bed completely.
They are vinyl and crinkle when you move. I move around a lot in my sleep but the sound seems to sooth me. The one that doesn't crinkle is about 14 bucks. I wet the bed when i get stressed. And these are a effective solution to keeping the mattress safe.