You spend about a third of every day in bed. Whether that time is spent blissfully slumbering -- or tossing and turning -- depends a lot on your mattress.

"A mattress can impact a person's sleep," says Michael Decker, PhD, RN, associate professor at Georgia State University and spokesman for the American Academy of Sleep Medicine.

One way that your mattress affects your sleep has to do with the network of fine blood vessels, called capillaries, that runs underneath your skin.

"When you lie on any part of your body for an extended period of time, the weight of it reduces the flow of blood through those blood vessels, which deprives the skin of oxygen and nutrients," Decker says. This causes nerve cells and pain sensors in your skin to send a message to your brain for you to roll over. Rolling over restores blood flow to the area, but it also briefly interrupts your sleep.

Ideally, a mattress that reduces the pressure points on your body should give you a better night's sleep, Decker says. Yet the ideal mattress is different for each person.