Why Sofa Bed Mattress Quality Matters

A sofa bed should not mean compromising on sleep.

At KHOY, we took a different approach to the sofa bed mattress. Rather than starting with a sofa mechanism and trying to make it comfortable enough to sleep on, we started with the mattress.

The result is a medium-firm foam mattress with a 4 cm memory-foam comfort layer,
designed to provide support while allowing the shoulders and hips to settle comfortably
into the surface.

Why choose a medium-firm mattress?

Many people assume that a very firm mattress is best for the back. Research suggests
that this is not necessarily the case.

A systematic review published in Sleep Health examined 24 controlled studies on mattress design. It found that medium-firm mattresses generally performed well for comfort, sleep quality and spinal alignment.[1]

A later systematic review of 39 studies reached a similar conclusion, finding that medium-firm mattresses can promote comfort, sleep quality and spinal alignment.[2]

The reason is relatively simple. A mattress needs to support the body without allowing it to sink too deeply, while still giving areas such as the shoulders and hips enough room to settle into the surface. A mattress that is too soft may allow excessive sinking, while a very hard surface can create uncomfortable pressure.

Medium-firm mattresses aim to balance these two needs.

Is a medium-firm mattress better for your back?

Research has also looked specifically at mattress firmness and lower-back discomfort.
A randomized, double-blind clinical trial published in The Lancet followed 313 adults with chronic nonspecific lower-back pain for 90 days. Participants who slept on medium-firm mattresses reported better outcomes for pain in bed, pain on rising and disability than those who slept on firm mattresses.[3]

More recent reviews also generally favour medium-firm mattresses over very soft or very firm options, although there is no single mattress firmness that is ideal for everyone.[2][4]

Body weight, body shape and sleeping position all affect how a person interacts with a
mattress. The aim is not to force the spine into a perfectly straight line, but to support its natural curves in a reasonably neutral position.[4][5]

Why does KHOY use 4 cm of memory foam?

Firmness is only one part of sleeping comfort.
The KHOY sofa bed mattress combines a supportive foam base with a 4 cm memory-foam layer on the sleeping surface. The two layers have different roles: the base provides stability, while the memory foam responds to pressure and adapts to the body.
This allows areas such as the shoulders and hips to sink slightly further into the surface
while the rest of the body remains supported. Research into mattress biomechanics also shows that comfort depends on several factors, including body shape, sleeping position, pressure distribution and spinal alignment.[5] 

Why trying the mattress at home matters

Research can help identify the qualities that generally support good sleep, but comfort is still personal. That is why trying a mattress in real life matters.

KHOY sofa beds come with a 90-day trial, giving you time to experience the mattress at
home and decide how its support, pressure distribution and everyday comfort feel to you.

Sources:
[1] Radwan A, Fess P, James D, et al. Effect of different mattress designs on promoting sleep quality, pain reduction, and spinal alignment in adults with or without back pain: systematic review of controlled trials.
Sleep Health. 2015;1(4):257–267. DOI: 10.1016/j.sleh.2015.08.001.

[2] Caggiari G, Talesa GR, Toro G, et al. What type of mattress should be chosen to avoid back pain and improve sleep quality? Review of the literature. Journal of Orthopaedics and Traumatology. 2021;22:51. DOI: 10.1186/s10195-021-00616-5.

[3] Kovacs FM, Abraira V, Peña A, et al. Effect of firmness of mattress on chronic non-specific low-back pain:
randomised, double-blind, controlled, multicentre trial. The Lancet. 2003;362(9396):1599–1604. DOI: 10.1016/S0140-6736(03)14792-7.

[4] Caggiari G, Petrucci F, Pescia S, et al. Mattress impact on lifestyle and back pain: a 25-year orthopedic literature review guideline. Journal of Orthopaedics and Traumatology. 2026. DOI: 10.1186/ s10195-026-00945-3.

[5] Wong DWC, Wang Y, Lin J, Tan Q, Chen TL, Zhang M. Sleeping mattress determinants and evaluation: a biomechanical review and critique. PeerJ. 2019;7. DOI: 10.7717/peerj.6364.