Adjustable width user support

Disclosed are apparatus and methodology for an adjustable width foam mattress which involves the use of modified lateral or side edges of an engineered foam mattress. Such lateral portions include collapsible structures for lateral adjustment of the overall width of the mattress. While different shapes are possible, one exemplary arrangement includes plural elongated octagonally-shaped openings. The long sides of such elongated structures form stops against each other as they fill the void of the opening. The relatively shorter sides of such structures articulate during collapse to accommodate such movement. As a result, and as the long sides fill in voids, the support structure essentially switches uniformly from one density to another, when moved from its expanded to its compressed position. An inflatable/deflatable member may be used to assist with expansion and compression of a lateral support structure.