In a 2003 Lancet randomised trial, people with chronic low-back pain on medium-firm mattresses had better results at 90 days than those on firm ones. Two systematic reviews, described below, also report results in favour of medium-firm mattresses. Which? adds a caution: the idea that a medium-firm mattress suits most people isn't always the case.
What "medium-firm" means
There is a research classification. The 2021 Journal of Orthopaedics and Traumatology review by Caggiari and colleagues grouped mattresses, following the European Committee for Standardization (2000), as soft, medium-firm, extra-firm, or mattresses customised for patients affected by supine decubitus.
The label in a shop is a different matter. Which? says many brands define firmness however they want, outside the official standard or with their own firmness scale, so you can't rely on those labels to compare firmness between brands. A "medium-firm" from one brand is a claim, not a measurement.
What the research found
The 2003 Lancet randomised trial (Kovacs et al.) started from a common belief: a firm mattress is often thought to help low-back pain, but the authors say evidence supporting that was lacking. They assessed 313 adults with chronic non-specific low-back pain who had backache in bed and on rising, and randomly assigned them to firm or medium-firm mattresses.
At 90 days, the people on medium-firm mattresses had better results for pain in bed, pain on rising and disability than those on firm mattresses. The authors concluded that a mattress of medium firmness improves pain and disability for people with chronic non-specific low-back pain.
A 2015 Sleep Health systematic review (Radwan et al.) included 24 articles and rated the quality of the trials moderate to high. It found that a mattress subjectively identified as medium-firm and custom inflated (self-adjusted) was optimal for sleep comfort, quality and spinal alignment. The same review notes that the literature disagrees on which type and features of mattress best reduce spinal pain and improve spinal alignment and sleep quality.
The 2021 review by Caggiari and colleagues included 39 articles and concluded that a medium-firm mattress promotes comfort, sleep quality and spinal alignment.
The 2009 Journal of Chiropractic Medicine study (Jacobson et al.) used a convenience sample of 59 healthy people with minor sleep-related aches and poor sleep. After baseline measures, their beds were replaced with new medium-firm beds, and the study reports significant improvements in sleep quality and efficiency.
Who it may not suit
Which? says that the claims that a medium-firm mattress suits most people, and that firm is better for back pain, aren't always true. In its buying guide, Which? says firmness comes down to personal preference.
If you have back pain that keeps you up or lasts, see a doctor or physiotherapist, as bed.chat advises; a mattress is buying guidance, not treatment.
Checks before you buy
- Read a brand's "medium-firm" label as that brand's own claim. Which? says you can't rely on brands' own firmness scales to compare firmness between brands.
For the other checks, such as size, base, trial terms and price, see the bed.chat checklist. For a personal answer, Bed Fit, the chooser on the bed.chat home page, asks nine quick questions and suggests a firmness range for how you sleep.
The trial and the two reviews above are the main research on medium-firm mattresses in this guide; the trial was in people with chronic low-back pain.
Sources
- Kovacs et al., The Lancet, 2003 (PubMed)
- Radwan et al., Sleep Health, 2015 (PubMed)
- Caggiari et al., Journal of Orthopaedics and Traumatology, 2021 (PubMed)
- Jacobson et al., Journal of Chiropractic Medicine, 2009 (PubMed)
- Which?: best mattresses for back pain
- Which?: best mattresses for side sleepers
- Which?: how to buy the best mattress