There have not been good studies looking into what type of mattress is best for people with back pain.

I don't believe there is just one type that is best. It is a very individual choice. In the past, doctors often recommended very firm mattresses. However, a study suggested that people who suffer from chronic back pain actually prefer a medium-firm mattress more often than a very firm one.

I usually suggest that people with back pain try sleeping on many different mattresses and beds to see if they can find a type that feels best. If you go to a hotel, or sleep at someone else's house, make note of how you feel after sleeping on the "new" bed.

Sometimes all you need is a plywood board under your current mattress. Try this before buying a new mattress. Also, try sleeping on a mattress on the floor. This will give the feeling of a "firm" bed. You might then have a better idea of what type of mattress you and your back prefer! Then you should go to a mattress showroom and try the mattresses before buying a new one.