One of the huge public health success stories of the past couple of decades has been the “Back to Sleep” campaign, which instructs parents to put their babies to sleep on their backs, not on their stomachs.
Since 1992, the year the American Academy of Pediatrics began recommending that babies sleep only on their backs (the official “Back to Sleep” campaign began two years later), the number of infants dying from SIDS (sudden infant death syndrome) has decreased in the United States by more than 50 percent.
“The less time infants spend on their stomachs, the slower they generally are to acquire motor skills during their first year, which means the potential delay of simple feats like lifting their heads as well as more complicated movements like rolling over, crawling, and pulling to stand,” writes Mossop. “Doctors have hesitated to sound the alarm about this since children usually walk shortly after their first birthday regardless of how much tummy time they’ve had. But a growing body of evidence now suggests that the timing of the motor-skill milestones that precede walking is crucial and can even factor into long-term health and cognitive ability.”
Mossop describes the research of a team of British scientists who have found that “the sooner children passed their prewalking motor-development marks, the better the more-complicated areas of their brains performed in later life. Every month in advance of the group average that a child learned to stand on his or her own translated to a half an IQ point increase at age 8. By age 26, early motor developers had higher reading comprehension. And by the time they hit their 30s, they had achieved a higher level of education and scored better on executive-function tasks like categorization — how fast they could group objects of similar shape and color.”
Far from a clear-cut conclusion
Mossop seems to be implying that now that babies are spending less time on their tummies and, thus, are developing motor skills later, they’re at risk of having lower cognitive skills as adults. I see several problems with leaping to that conclusion. Most notably, the research he describes is observational — it shows only an association between earlier-than-average motor development and stronger cognitive skills later in life, not a cause-and-effect relationship. Other factors — ones the studies weren’t designed to identify and that have nothing to do with motor skill milestones — may have influenced the results. (University of Minnesota researchers reported last month, for example, that babies who got most of their sleep at night rather than during daytime naps scored better as toddlers on several cognitive tests.) Futhermore, as the researchers themselves acknowledge in the studies Mossop cites, any observed cognitive differences between people who passed their motor skill milestones early and those who passed them later was often quite small.
It seems highly unlikely that post-1992 generations are going to have weaker cognitive abilities than their parents and grandparents simply because they spent their initial months sleeping on their backs and thus reached motor-skill milestones at slightly later age markers.
Indeed, as Mossop notes, other research has found the lag in pre-walking motor-skill development by back-sleeping babies to be inconsequential.
What doctors advise
Still, the American Academy of Pediatrics recommends that parents give their babies regular tummy time — only while the child is awake — to develop upper body strength and to prevent flat spots from forming on the back of the baby’s skull. Not all parents are getting the tummy time message, however. A study published earlier this year in the Journal of Pediatric Health Care found that although 90 percent of new mothers are being properly instructed on the need to put their newborns to sleep on their backs, only 55 percent are being told that their babies need supervised playtime on their tummies.
Doctors recommend that tummy time start for most infants as soon as they’re brought home from the hospital. “With babies who are too young to support their own heads, parents can lie down and cradle them on their chest, introducing the stomach position in a comforting way,” reports Mossop. “When infants get older and get the head-lifting thing down, regularly placing toys around their field of view encourages them to look around and stretch. It’s pretty basic, really. And if babies cry because they’re not used to the stomach position, stick with it for a bit anyway. The long-term benefit is worth the short-term fuss.”
You can read Mossop’s article here.