Long discouraged by some, the pacifier actually lowers risk of sudden infant death syndrome, or SIDS, new research has shown.

The findings reinforce recommendations made recently by the American Academy of Pediatrics that pacifiers be used at nap and bedtimes in the first year of life.

A decade ago, a successful public health campaign to get infants off their stomachs when sleeping – and on their backs – cut the SIDS rate in half. In 2002, 2,295 babies were diagnosed at death with SIDS. Before that, it was estimated that 5,000 babies a year were lost to SIDS.

The newly published pacifier research “is a very strong finding,” said Dr. Fern R. Hauck, associate professor of family medicine at the University of Virginia Health System. “The body of evidence kept growing,” added the pediatrician, who reviewed the studies in the journal Pediatrics last month.

In the latest study, published in the British Medical Journal, Dr. De-Kun Li and his colleagues at Kaiser Permanente in Northern California, in collaboration with researchers at the National Institutes of Health, interviewed 185 mothers who had just lost their infants to SIDS and 312 mothers whose babies were developing normally. All the mothers were from California.

Use of a pacifier, the scientists reported, reduced the risk of SIDS by 90 percent.

Li said there are several possible explanations. One is that sucking enhances alertness, which is regulated by a brain center that some scientists have shown is not working properly in children at risk for SIDS, in which otherwise healthy infants suddenly stop breathing. If this were the sole explanation, then thumb-sucking would offer the same protection, and it doesn’t, Li said.

His favorite hypothesis, which he is now setting out to prove, is that the pacifier serves as a mechanical barrier between the infant’s mouth and any potential for blocked airways, such as soft bedding.

“The pacifier stops suffocation,” Li said. “It is more mechanical and physical, rather than biological.”

Whatever the reason, Hauck and others say that a new push to promote pacifier use during sleep throughout the first year could lower the SIDS rates even more. The last decade’s “Back to Sleep” campaign, based on the link between SIDS and babies suffocating on blankets or soft bedding, has been the first intervention to dramatically save lives. Add a pacifier and the risk is even lower, Li said.

Doctors say breast-feeding mothers should establish good nursing habits before providing their infant with a pacifier during sleep – and only during sleep, Hauck said.

She said the new recommendation is being hotly debated among some parent groups. There have been a few studies that suggest pacifier use could cut down on an infant’s wish to breast-feed, although Hauck says there are just as many studies that find no such effect. Others are afraid that pacifiers will lead to dental problems, but Hauck said that a year of pacifier use, well before permanent teeth emerge, has no effect on the way the teeth grow in.