The invention relates to an adjustable-width mattress comprising a central portion, that includes pneumatically-separated first center air cells and second center air cells； the first center air cells are pneumatically connected to a first expansion portion by first air channels； the first expansion portion includes a first outer cell and a first inner cell； the first outer cell and the first inner cell each encapsulate, respectively, a first and second foam element； the first outer cell and the first inner cell are attached to each other at a hinge line.
