Are All Mattresses Basically Made Equal?

What the research showed

Ren et al. (2023) tested mattresses built from the same filling materials but arranged in different layer orders. The result was unambiguous: layer order alone changed every key performance metric.

Mattresses with hardness increasing from top to bottom — softest layer at the surface, progressively firmer toward the support core — consistently outperformed the reverse arrangement:

• Larger low-pressure area — more of the body in a comfortable zone
• Smaller high-pressure area — fewer painful pressure points
• Lower maximum and average pressure — better load distribution overall
• Higher subjective comfort scores — sleepers felt the difference

Same materials. Different order. Measurably different results.

Why layer order matters

Each layer of a mattress has a specific job:

• Top layer — should be soft enough to contour bony prominences and relieve pressure
• Middle layers — should manage the transition between surface compliance and deeper support
• Support core — should be firm enough to resist collapse and maintain spinal alignment

When layers are reversed — firm on top, soft underneath — both jobs fail simultaneously. The hard top creates pressure points; the soft bottom allows instability rather than support.

Why "foam" or "hybrid" is not enough information

Wong et al. (2019) make the same point from a biomechanical direction: mattress evaluation depends on design features, pressure distribution, alignment, and body-specific interaction — not material category alone.

Two mattresses sharing the same label — "memory foam," "hybrid," "medium-firm" — can perform very differently. The label tells you what materials may be present. It tells you almost nothing about how those materials are arranged or what the construction will deliver under your body.