The team excluded infants with known birth defects and infants born between 1994 and 1996, when the Back to Sleep campaign was just starting; this gave the researchers two clear pre- and post-campaign groups to compare. They then separated the infants into three groups based on the elevation of the babies&apos; homes: less than 6,000 feet (1,828 m), between 6,000 and 8,000 feet (1,828 m to 2,438 m), and above 8,000 feet (2,438 m).
The researchers controlled for a slew of demographic and social factors, including infant health and breastfeeding status, whether the baby&apos;s mother smoked during pregnancy, and parental age, race, education and socioeconomic status.
The researchers emphasized that even at high elevations, the risk of SIDS is still low. Even above 8,000 feet, a baby&apos;s chance of dying of SIDS is only 0.079 percent.
"I think it&apos;s important to point out that parents can still focus on modifiable risk factors for sudden infant death syndrome, including putting infants on their back to sleep, avoiding excessive blankets or stuffed animals, and maintaining a no-smoking environment," Katz said.
"I would like parents to feel that they&apos;re empowered to take some very concrete steps to minimize risk of SIDS wherever they live," study co-author Dr. Susan Niermeyer, a professor of pediatrics at the University of Colorado School of Medicine, told Live Science. Breastfeeding and sleeping in the same room as an infant can also reduce SIDS risk, she said.
If their babies object to back-sleeping, parents can be reassured that once a baby is strong enough to roll onto his or her own stomach, parents don&apos;t need to keep flipping the baby back over all night.
"If they&apos;re able to turn over, they&apos;re probably going to have the motor development to get themselves out of a situation where they have an obstructed airway," Niermeyer said.
She did recommend that parents take caution in traveling to high elevations during the first month or two of an infant&apos;s life, but not because of SIDS. Just like adults, she said, babies can come down with altitude sickness because of the lower density of oxygen in thin mountain air.
The researchers emphasized that their study was observational, so researchers can&apos;t be sure why elevation and SIDS appear to be linked. "I&apos;m going to resist the urge to speculate," Katz said.
But the hypoxia of high elevation is a useful way for researchers to explore the potential causes of SIDS in experimental or animal studies, Niermeyer said. It&apos;s possible that lower oxygen levels affect the prenatal development of the nervous and respiratory systems, or that there are effects after birth, she said.
The team excluded infants with known birth defects and infants born between 1994 and 1996, when the Back to Sleep campaign was just starting; this gave the researchers two clear pre- and post-campaign groups to compare. They then separated the infants into three groups based on the elevation of the babies&apos; homes: less than 6,000 feet (1,828 m), between 6,000 and 8,000 feet (1,828 m to 2,438 m), and above 8,000 feet (2,438 m).
The researchers controlled for a slew of demographic and social factors, including infant health and breastfeeding status, whether the baby&apos;s mother smoked during pregnancy, and parental age, race, education and socioeconomic status.
The researchers emphasized that even at high elevations, the risk of SIDS is still low. Even above 8,000 feet, a baby&apos;s chance of dying of SIDS is only 0.079 percent.
"I think it&apos;s important to point out that parents can still focus on modifiable risk factors for sudden infant death syndrome, including putting infants on their back to sleep, avoiding excessive blankets or stuffed animals, and maintaining a no-smoking environment," Katz said.
"I would like parents to feel that they&apos;re empowered to take some very concrete steps to minimize risk of SIDS wherever they live," study co-author Dr. Susan Niermeyer, a professor of pediatrics at the University of
 Colorado School of Medicine, told Live Science. Breastfeeding and sleeping in the same room as an infant can also reduce SIDS risk, she said.
If their babies object to back-sleeping, parents can be reassured that once a baby is strong enough to roll onto his or her own stomach, parents don&apos;t need to keep flipping the baby back over all night.
"If they&apos;re able to turn over, they&apos;re probably going to have the motor development to get themselves out of a situation where they have an obstructed airway," Niermeyer said.
She did recommend that parents take caution in traveling to high elevations during the first month or two of an infant&apos;s life, but not because of SIDS. Just like adults, she said, babies can come down with altitude sickness because of the lower density of oxygen in thin mountain air.
The researchers emphasized that their study was observational, so researchers can&apos;t be sure why elevation and SIDS appear to be linked. "I&apos;m going to resist the urge to speculate," Katz said.
But the hypoxia of high elevation is a useful way for researchers to explore the potential causes of SIDS in experimental or animal studies, Niermeyer said. It&apos;s possible that lower oxygen levels affect the prenatal development of the nervous and respiratory systems, or that there are effects after birth, she said.