Hard mattresses not best for back pain.

Mattresses rated medium-firm are better for people with chronically sore backs than are firm mattresses, researchers in Spain find. Their report in the Nov. 15 Lancet contradicts the long-held view that harder is better when it comes to beds and backs.

The scientists randomly assigned 158 people to use firm mattresses and 155 to sleep on medium-firm mattresses. The mattresses--which met European standards for firmness--were delivered to the homes of the volunteers, all of whom were adults with a long history of lower-back pain. The participants rated their pain before the study and after 90 days, using a standardized scale.

People sleeping on the medium-firm mattresses had significantly less pain upon arising in the morning and less overall disability from their back pain than did people using the firm mattresses, reports a group led by Francisco M. Kovacs, a physician at the University of Barcelona and the Kovacs Foundation in Palma de Mallorca.

Although the reason for the differences remains unclear, questionnaire data show that 69 percent of the volunteers that had slept on medium-firm mattresses slumbered mainly in the fetal position by the end of the study, compared with 59 percent of the other study participants.

A fetal position may produce less back pain than other positions do, speculates Jenny McConnell of the University of Melbourne in Parkville, Australia, in the same journal. The new study suggests that doctors "may be confident in recommending a mattress of medium firmness" to patients with bad backs, she says.--N.S.