Is a harder or softer mattress better for back pain?

If you have a bad back, you should buy the firmest mattress you can find -- right? Not so fast. While that used to be the common wisdom, there's no solid research behind it. The latest thinking is that there isn't one type of mattress that's best for everyone, including people with chronic back pain. Let personal preference guide you, and choose what feels most comfortable.

But making the right choice can be tricky. So many products are on the market, and just because a mattress feels good when you lie down on it in a showroom doesn't mean you're going to be happy sleeping on it for the next several years.

Here are a few tips to guide you:

It Needs to Keep Your Spine Aligned

You may not realize it, but good posture is important when you sleep. The muscles and ligaments (tissue that holds joints together) in your back need to relax and recover while you snooze. If a mattress is too firm -- or too squishy -- it won't support your spine at your neck or lower back the way it needs to. What's firm enough (but not too firm) is different for everyone: If you have wide hips, for instance, a slightly softer surface may be better. You need some more give in order to keep your spine in alignment. Someone with narrower hips might be better off with a firmer surface.

When in Doubt, Go ‘Medium-Firm’

Research is limited, but in one study, researchers assigned new mattresses to more than 300 people with low back pain. They used either "medium-firm" or "firm" mattresses for 90 days. Those in the medium group reported the least amount of discomfort.

You might consider getting a memory foam mattress (instead of a traditional innerspring one). The foam molds to your body. The downside: Some memory foam mattresses keep in heat; and the material might have more chemicals.

Take a Longer Test-Drive

If you have a great night's sleep and wake up pain-free after staying at a hotel or in a friend's guest room, copy down that mattress's model number. Or choose a mattress that comes with a money-back guarantee: A growing number of companies will let you buy a mattress and use it for anywhere from 30 to 100 days and send it back for a refund if you're not happy with it.

Just Buy Something

When researchers from Oklahoma State University randomly assigned 62 people to sleep in a variety of new beds for 28 days, they found that almost everyone started to sleep better. That was true regardless of which model they were given, though people who slept in the cheapest beds did report more lower back pain than those in the medium- and higher-priced beds.

The most important thing seemed to be that the beds were new. They noted that the average age of the participants' old beds was 9.5 years. And they concluded that "sleep quality may be dependent on timely replacement of bedding systems." The takeaway: If you've been sleeping on the same mattress for 9 or 10 years (or more), it's time to get a new one. Almost any new replacement is going to be better than the saggy foundation of an old mattress. But it may pay to spring for at least a mid-priced model.

Pillows and Positions Matter

Even if you have the right mattress, it’s not the only thing that counts when it comes to managing your back pain as you rest. Sleep position is important, as are the kind of pillows you use and where you place them.