A New Series on the "Back to Sleep" Recommendation to Reduce SIDS

Is the evidence implicating the prone position strong enough to merit the public policy campaign that puts all babies to sleep on their backs?

Hi everyone. It is John. I am pleased to once again feature writer and economist Elizabeth Fama, PhD, who delved into the evidence underpinning the recommendation to place babies on their back to sleep.

Her critical appraisal is a tour de force in everything we love here at Sensible Medicine. I had no idea how weak the evidence was for this recommendation.

Ms. Fama’s series includes many of our favorite topics—doubts regarding plausibility, confounding in observational data, competing causes of outcomes, and, for the win, inadequate consideration of the downsides of a sweeping recommendation.

We will publish this series in four parts. I plan to interview Ms. Fama and have a podcast at the end.

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Part I

Is “Back to Sleep” Really Best?

By Elizabeth Fama

My first two children slept on their tummies as infants, uncontroversially. Dr. Spock endorsed stomach sleeping, my mother had slept my siblings and me that way, and my babies vastly preferred it.

But, beginning in the early 1990s, just before my third and fourth children were born, medical associations and the U.S. government launched a campaign called “Back to Sleep,” now rebranded as “Safe to Sleep,” urging me to sleep my babies on their backs.

The reason: putting babies to sleep on their tummies could cause SIDS, sudden infant death syndrome, every parent’s nightmare. I felt like a child endangerer when, exhausted and desperate for my own sleep, I rolled the next two fussy babies from their backs onto their bellies within a couple of weeks of their births. I vividly remember whisper-sobbing: please don’t die. They slept well and thrived.

When our first grandchild arrived, her parents and I dutifully put her on her back. Over the next six months, the baby’s sleep was so poor that my daughter wondered whether she might have a genuine sleep disorder. I also noticed that, although the baby was smart and engaged, she was weaker than her mom had been at each age, and she was hitting her gross-motor milestones much later. Was it due to individual variation in strength and motivation, or could back sleeping have something to do with it, or both?

I fell down a rabbit hole of research: What is the evidence about sleep position and SIDS? Are there costs to back sleeping? Does it make sense to apply the same advice unconditionally to all babies?

I learned that there are potential downsides to sleeping babies on their backs. Babies have less deep sleep on their backs, depriving their growing brains of needed rest. Skulls can become flattened. Infants who sleep on their backs (supine) develop muscle tone more slowly. They take longer to hold their heads up, roll over, sit unsupported. “Safe” sleep may be ruining sleep so terrifically for babies and parents that a multi-billion-dollar commercial industry has arisen, made up of sleep consultants, proto-medical devices, and rocking bassinets. And I’ve begun to wonder whether the skyrocketing rates of postpartum depression could be related to lack of sleep for moms.

The evidence that back sleep protects against SIDS, on the other hand, turns out to be weaker than I expected—for many reasons.

• No one has found a mechanism that explains SIDS, or that makes stomach (prone) sleep itself unsafe.

• The scientific literature is based on observational studies, not randomized controlled trials.

• Multiple sleep recommendations were introduced along with back sleep, confounding a causal interpretation in the data.

• There are many other risk factors for SIDS that dwarf prone sleep as a primary risk.

• Researchers observe that SIDS rates declined as more parents took the back-sleeping advice, but the drop is also coincidental with many other changes. For instance, over the same period, vaccinations improved, pollution decreased, more mothers breastfed, there were fewer teen births, more people stopped smoking, and baby equipment got safer. Child and infant deaths of all causes declined.

• Scientists acknowledge that the statistics on how many babies die of SIDS vs. other causes are unreliable because coroners classify deaths differently, and the quality of investigations varies.

• Improvement in SIDS rates stubbornly plateaued around 1997, even as more parents followed the advice to sleep babies on their backs.

• A substantial number of SIDS babies still die on their backs.

In short: sleep position seems to be one of many interventions that change small probabilities; and sleeping on the back may not be costless.

My goal in this series is to describe what I learned.

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Sleep-Position Recommendations Over Time

Before 1992, most babies in the U.S. slept on their stomachs. A national survey that year showed that only 13% slept wholly on their backs (Figure 1). Healthcare professionals recommended tummy sleep or side sleep to prevent the infant from choking. Dr Spock suggested that pressure on the abdomen also relieved gas pains, and prone sleep prevented flattening of the skull (my edition: Baby and Child Care, 26^th Edition, November 1974, section 257).

Many SIDS researchers claim that back sleeping was more common before the 1950s, and that unscientific recommendations in baby-care books caused parents to change to tummy sleeping, but I have not found data to support or refute that claim. Certainly, throughout prehistory and history (and today in many countries), women have co-slept with their babies, which implies more side sleep (face-to-face) and supine sleep than prone.

Co-sleeping surely was the only way of putting a baby to sleep throughout most of human evolution, argues James J. McKenna, a biological anthropologist at Notre Dame. The earliest small cradles and baskets look as if they require supine sleep. What we think of as cribs, with bars and mattresses, began to be fabricated in the 19^th century, at which time front sleeping an infant may have become more ubiquitous in western societies.

In 1992, spurred by a growing body of research primarily in Australia and Great Britain, the American Academy of Pediatrics (AAP) recommended that babies be put to sleep on their backs or sides to prevent sudden unexpected infant deaths, and the first U.S. studies began to appear. The National Institute of Child Health and Human Development (NICHD) launched its “Back to Sleep” campaign in 1994, based on the 1992 AAP guidelines—that is, “back or side” was recommended.

Several other sleep recommendations quickly followed: firm sleep surfaces, no soft bedding or toys in the crib, avoid maternal smoking prenatally or in the household postnatally, a cool room, breastfeed if possible, no co-sleeping with the infant, but have the baby in the same room with you, and don’t sleep on the couch with the baby. The AAP allowed side sleeping until 2005, but only as a discouraged second-best alternative to the back. The campaign was rebranded “Safe to Sleep” in 2012, to reflect the emphasis on more than just sleep position.

Figure 1. Rate of SIDS and solely back sleeping (not back plus side). This graph, originally from the NICDH website, is no longer available except in the “Safe to Sleep” entry on Wikipedia.

By 2006, the National Infant Sleep Position household survey showed that 75% of U.S. babies were sleeping wholly on their backs (Figure 1). The decline in SIDS deaths seemed to confirm the wisdom of the advice.  

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In next week's post, Ms. Fama explores the potential downsides of sleeping babies on their backs. She also notes the downstream effects of this recommendation.