Effect of Mattress Firmness on Chronic Low-Back Pain: A Randomised, Double-Blind Controlled Trial
Study by F. M. Kovacs, V. Abraira, A. Peña and 10 co-authors (full list in the citation below)
Randomised Double-Blind Trial · The Lancet (Vol. 362, Issue 9396, pp. 1599-1604) · DOI: 10.1016/S0140-6736(03)14792-7
Key Takeaway
Medium-Firm Beat Firm for Pain in Bed and Disability at 90 Days
What was tested: 313 adults with long-term low back pain that had no clear cause, and who had backache in bed and when getting up, were randomly given either a firm mattress or a medium-firm one. Neither the patients nor the people assessing them knew which mattress each person had (study abstract).
What the numbers showed: At 90 days, the medium-firm group had better odds of improvement in pain while lying in bed (odds ratio 2.36) and in disability (odds ratio 2.10). For pain on getting up, the 90-day result (odds ratio 1.93) was not statistically clear.
What this means for you: For these patients, a medium-firm mattress did better than a firm one. The trial compared only two mattresses of set firmness. It did not test modern foam or hybrid beds, and it did not test any brand you can buy today.
Key Numbers
How the Study Was Done
This was a randomised, double-blind, controlled trial run at several centres and published in The Lancet in 2003. It enrolled 313 adults with chronic non-specific low back pain, which means long-term pain with no single clear cause. Everyone had backache while lying in bed and on rising, and none had pain spreading down the leg (Kovacs et al., 2003).
Firmness was rated on a scale set by the European Committee for Standardisation. The scale runs from 1.0 (firmest) to 10.0 (softest). Each person was randomly given either a firm mattress rated 2.3 or a medium-firm mattress rated 5.6. The study team assessed everyone at the start and again at 90 days. The main outcomes were changes in pain while lying in bed, pain on rising, and disability in daily life (The Lancet).
What the Study Compared
Medium-Firm (5.6 on the European Scale)
Better odds of improvement in pain in bed and in disability at 90 days than the firm group.
Firm (2.3 on the European Scale)
The comparison group. Over the whole study, this group reported more pain on rising than the medium-firm group.
What the Study Found
At 90 days, people on medium-firm mattresses had better outcomes than people on firm mattresses for pain in bed (odds ratio 2.36, 95% confidence interval 1.13 to 4.93) and for disability (odds ratio 2.10, 1.24 to 3.56). For pain on rising, the odds ratio was 1.93, but its range (0.97 to 3.86) includes 1. That means the 90-day result for pain on rising was not statistically clear (study abstract).
An odds ratio compares the odds of improving in one group with the odds of improving in the other. An odds ratio of 2.36 means the odds of less pain in bed were about 2.4 times higher on the medium-firm mattress. It does not tell you how much less pain people had.
Looking across the whole study period, the medium-firm group also reported less pain on rising (p=0.008). The differences for daytime low back pain (p=0.059) and pain while lying in bed (p=0.064) were smaller and did not reach the usual 0.05 cut-off. The authors concluded that a mattress of medium firmness improves pain and disability in people with chronic non-specific low back pain (study abstract).
The trial did not test modern memory foam, latex or hybrid mattresses, and it did not test any brand sold today. It measured pain and disability. It did not measure muscle activity or spinal position during sleep.
How to Apply This Study When Choosing a Mattress
What to look for: A mattress sold as medium-firm, if you have long-term low back pain.
Brands rate firmness in their own way, and none of them use the scale from this trial. Treat a brand's firmness label as a rough guide, and use the sleep trial and return window to judge how your back feels.
Study Scope and Limitations
The trial included adults with chronic non-specific low back pain who had backache in bed and on rising, and no pain spreading down the leg. It compared only two mattresses of set firmness over 90 days. It did not test modern foam or hybrid beds, or any brand.
Primary Citation
Kovacs, F. M., Abraira, V., Peña, A., Martín-Rodríguez, J. G., Sánchez-Vera, M., Ferrer, E., Ruano, D., Guillén, P., Gestoso, M., Muriel, A., Zamora, J., Gil del Real, M. T., & Mufraggi, N. (2003). Effect of firmness of mattress on chronic non-specific low-back pain: randomised, double-blind, controlled, multicentre trial. The Lancet, 362(9396), 1599-1604.