“Compared to back and stomach sleepers, side sleepers require additional support because they have a larger gap between their head and the mattress” while lying on their side, says chiropractor Dr. Randi Jaffe. She explains that the shape of a cubed pillow better fills this gap and helps prevent side sleepers from collapsing or scrunching up their shoulder, which can result in misaligned joints and tight muscles. The shape, she says, “is designed to fit perfectly in the gap between your shoulder and your ear, supporting your neck, which reduces strain and allows the spine to remain in a neutral and aligned posture during sleep.”
Chiropractor Dr. David Perna of Back and Body Medical agrees that a “cubed pillow makes sense” for side sleepers, as the shape “will allow less stress on the neck and bottom shoulder.” But Jaffe cautions that cubed-shaped pillows are really best for true side sleepers — not combination sleepers who roll onto their stomachs or backs, because its shape can actually make sleeping in those positions less comfortable.