A bed is described having a mattress or mattress, wherein the mattress has at least two rests arranged on two sides of the mattress parallel to each other, the rests being adapted to be arranged on respective lifting mechanisms intended to bring the mattress into a position such that it can be rotated on itself by 180° about a horizontal axis. According to the invention, the rest support is formed by two extendible elements which converge to form a joint with lower ends attached to the frame at a distance, the floor or the ceiling and at whose top a support is formed for the rests.