Researchers at the Korea Research Institute of Standard and Science in Yuseong, South Korea, got closer to an answer. They measured study participants’ spinal curvature and pressure on different mattresses, then asked the subjects to evaluate the mattresses. They found that the participants preferred mattresses on which the spinal curvature when lying down was similar to their spinal curvature when standing.^[4]

They also looked at pressure differently, examining the range of distribution of body pressure rather than maximum pressure. Participants were more comfortable when this range was narrow, the researchers found.^[4]

Using these criteria, some of the same researchers went on in a new study to test the relationship of sleep quality to these factors. They didn’t just obtain measurements on the 16 study participants as the participants lay on a mattress; they kept them for 6 days and nights in a sleep laboratory. There, the researchers used electroencephalography, electromyography, electrooculographics, and sensors to measure the participants’ brain waves, eye movements, chin movements, heart rhythm, and body temperature.^[5]

They found that when the participants slept on mattresses that were deemed “comfortable,” on the basis of spinal curvature and distribution of pressure, their sleep efficiency and percentage of deep sleep were higher, and the percentages of time that they woke up after going to sleep were lower.

What about firmness? In a survey of orthopedic surgeons, 95% believed that mattresses played a role in the management of low back pain, and 76% recommended a firm mattress.^[6]

From that finding, one might conclude the firmer the mattress, the better. A group of researchers at the Kovacs Foundation in Palma de Mallorca and six other Spanish centers put that notion to the test by randomly assigning 313 adults with chronic, nonspecific low back pain to either a firm mattress or a medium-firm mattress.^[8] After 90 days, the patients with medium-firm mattresses had better outcomes for pain in bed, pain on rising, and disability than the patients with firm mattresses.

Putting these findings together, it would seem doctors should recommend mattresses that do not distort their patients’ spines, distribute weight evenly, and are medium-firm in density.

Advice for Patients

Of course, few patients can bring specialized testing equipment with them to mattress stores. So it may be hard for them to know how much their spines curve and how well their weight is distributed when they lie on a mattress.

But, as the Korean team pointed out, these factors and the subjective sensation of comfort correlate. So the commonsense approach to selecting a mattress may still be the best advice.

“I would just go by what feels comfortable to me,” said Dr DeVocht. “I would lie on it.”