Medium or firm mattress for back pain? What the evidence and our showroom both say

Short answer: medium-firm, for most people. Not firm. The idea that a bad back needs a hard bed is one of the most persistent myths in furniture, and it sends a lot of people home with a mattress that makes them worse.

What the research says

The best-known study on this, a Spanish trial published in The Lancet in 2003, gave people with chronic low-back pain either a firm mattress or a medium-firm one for three months. The medium-firm group reported less pain in bed, less pain getting up, and less disability during the day. Later reviews have broadly agreed: medium-firm is the sensible default for back pain, and very firm is not.

That fits what we see on the showroom floor. The people who insist on the firmest mattress we have are usually back a year later saying their hips hurt.

Why firm alone does not work

Your back needs two things from a mattress. Support, which is the springs underneath holding your spine level. And pressure relief, which is the surface giving way under your hips and shoulders so they are not carrying all your weight. A very firm mattress gives the first and refuses the second. On your side, your hip and shoulder take the load, go numb, and you turn over. On your back, the small of your back is left hanging in a gap.

Medium-firm gives support from the springs and enough give at the surface to let the heavy bits sink slightly, so the spine stays straight. That is the whole trick.

How to tell what you need

Side sleepers need more give at the surface than back sleepers, because the hip and shoulder stick out further. If you sleep on your side and choose firm, expect a sore shoulder.

Back sleepers can go a little firmer, but still want the surface to fill the curve of the lower back rather than bridge it.

Heavier people (roughly 16 stone and up) sink further into any mattress, so a firmer one gives them the feel a lighter person gets from a medium. Firmness labels are relative to weight.

Couples of different sizes should ignore the label entirely and lie on it together. Pocket springs are what let two people of different weights share one mattress without one rolling into the other.

The test that actually works

Lie on the mattress in the showroom in the position you sleep in, for ten minutes, not thirty seconds. Then get a hand under the small of your back. If it slides in easily on your back, the mattress is too firm for you. If your hips and shoulders feel like they are pressing against something on your side, same again. Comfortable, held, nothing pressing, nothing sagging: that is the one.

What we point people at

For back pain we usually start people on the Garscadden 3400, medium to firm with 3,400 pocket springs and a pressure-relieving Zero Gravity layer, or the Ted 1000 for lighter frames and side sleepers. Sealy fans can try the Grasmoor, which is a proper firm, and compare it side by side with the medium Blake. All of them are on the floor in our Clydebank showroom.

If you still want the firmest thing we have, we will sell you it. But lie on the medium-firm one first.

Paul James Home, Co-op Department Store, Clydebank. Monday to Saturday 9 to 5. 0141 266 0400.