(Reuters Health) - While a nationwide push to get babies to sleep on their backs initially produced steep declines in unexplained and sleep-related infant deaths, U.S. progress against these fatalities has been minimal in recent years.

In 2015, about 92 in every 100,000 babies up to age 12 months died of sleep-related causes like sudden infant death syndrome (SIDS) or accidental suffocation and strangulation in bed or other unknown causes, researchers report in Pediatrics. That’s down from about 155 deaths for every 100,000 babies in 1990.

But most of this progress occurred before 2000. Deaths rates plunged by 45 percent from 1990 to 1998 and then dipped by just 7 percent from 1999 to 2015.

“We still have 3,500 babies dying from sleep-related deaths every year in the U.S., and our rates are higher than most other industrialized countries. We lose one baby every two to three hours every day of the year,” said Dr. Michael Goodstein of WellSpan Health in Pennsylvania who wasn’t involved in the study.

“It is national tragedy,” Goodstein said by email.

SIDS has become much less common in recent decades as doctors have urged parents to put infants to sleep on their backs without blankets or other soft bedding and toys that could pose a suffocation risk. But it still remains a leading cause of infant mortality, according to the American Academy of Pediatrics (AAP).

These deaths can be caused by a variety of factors including brain abnormalities or respiratory problems in babies as well as sleeping face down on fluffy surfaces or surfaces that pose a risk of suffocation.

To reduce the risk, the AAP recommends that babies sleep in the same room as their parents – but not the same bed – for at least six months and ideally up to one year.

Breastfeeding can also help prevent SIDS, but mothers shouldn’t sleep with babies in their beds to make nursing more convenient in the middle of the night, according to the AAP guidelines.

From 1999 through 2015, infant death rates from accidental suffocation and strangulation in bed surged 184 percent, the study found. This happened as declines in the use of soft bedding slowed, gains in getting babies to sleep on their back halted, and sharing beds with parents increased.

Since 1999, progress has also varied by state.

In the District of Columbia, for example, the number of deaths for every 100,000 babies dropped by 82 cases since 1999, to 102 per 100,000 by the end of the study.

At the other extreme, in Alaska, the number of deaths climbed by 55 cases per 100,000 during this time to 202 fatalities for every 100,000 babies.

Many factors may have contributed to differences among the states, including varying levels of regulation and education about safe infant sleep practices, said lead study author Alexa Erck Lambert, a researcher for the U.S. Centers for Disease Control and Prevention in Atlanta.

“The role of these sudden unexpected infant death risk reduction programs, demographic changes, tobacco use, and emerging issues such as increasing opioid use, deserve further investigation,” Lambert said by email.

One limitation of the study is that it relied on death certificate records, which may not always accurately reflect the reasons babies died, the authors note.

Still, the results offer fresh evidence that the U.S. has a long way to go in reducing these deaths, said Anna Pease, a researcher at the University of Bristol in the UK who wasn’t involved in the study. One fix might be to adopt an approach similar to the UK, which focuses on safe practices for bed sharing instead of on discouraging the practice outright, Pease said by email.

“They must never sleep on a sofa or in a chair with another sleeping person, and avoid bed sharing if there is any smoking, drinking or drugs involved, or if the baby was preterm or low birth weight,” Pease advised. “Parents can further reduce the risks by being smoke-free during and after pregnancy, breastfeeding if they can, and making sure the baby does not get too hot or too cold.”

SOURCE: bit.ly/2suicJQ Pediatrics, online February 12, 2018.