Links - SIDS (don't look away)

Tragedy demands more attention.

Sensible Medicine just concluded a guest-post series on SIDS. For all the reasons SM is interested in it, I was too.

This series has a lot of great applied lessons and otherwise challenges the conventional wisdom. As the Sensible Medicine folks write,

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.

In Post #1 she summarizes this journey thusly:

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.

In Post #2 we (re)learn some hard lessons. There are ALWAYS hidden costs that must be considered with any policy. In this case it includes poor sleep quality, Positional Plagiocephaly (a flattening of the baby’s head that can result from exclusive back-sleeping), and delayed milestones.

On that last point, Dr. Fama notes,

Rather than investigate the potential health implications of delayed milestones, medical authorities seem to have pushed back expectations of those skills.

Additionally we have the lesson of emergent supporters in the form of the cottage industry that has crept up as a result of the byproducts of the Back to Sleep movement. These are now enormous-revenue industries that have strong vested interest in maintaining the status quo. This is certainly a Bootleggers and Baptists story.

Among other confounders worth pondering are two considered in Post #3: a redefinition of a SIDS death as well as simply the potential that the decline in SIDS was coincident to rather than caused by Back to Sleep.

Goldstein, et al. show that the rate of SIDS has declined almost exactly apace of the decline in overall deaths, except for a brief window between 1994 and 1996 where SIDS declined faster than other causes of death, which they attribute to Back to Sleep. The effect disappears entirely after those couple of years.

For those of us who understand the meme, this picture springs to mind when reading Post #4:

Asking about the conditions present when X happens is not a reliable way of determining if those conditions cause X. The fact that the thief was driving a yellow car does not support the idea that banning yellow cars or prescreening cab drivers will lead to less theft. We need to know a lot more about thieves, cars, and the interaction effects between them.

On its own, the Kassa et al. data above might suggest to you that prone sleep is even more dangerous than expected: babies reported as dying on their backs were really on their stomachs. But SIDS is a rare event, and these data only tell us, of babies who died, what fraction were placed or found prone vs. supine? The question we want to know is, of babies who are placed prone or supine, what fraction die?

As an extreme example: if 3 out of 4 babies who died were found on their stomachs, it seems to imply that tummy sleeping is dangerous. Yet suppose that among all babies, 9 out of 10 were sleeping on their stomachs. Now we would conclude that prone sleep is in fact safer than supine. More of the babies who were sleeping on their backs died. If parents skew their answers toward supine sleep, we get a biased measure of the dangers of prone sleep. The paper by Kassa et al. seems to show that this bias exists.

The threat of SIDS has all the hallmarks of a rush for solutions without consideration for calm, rational, constructive debate. It is a combination of very rare and extremely binary (either a baby is dead or a baby is not dead and there aren't even close calls like in drowning), all the while being incredibly terrifying (a phantom menace is lurking that might silently take your child in the night). Once we have enough evidence, the motivated desire to both coalesce around consensus and double down against questions of that consensus is very strong.

Nuance has no welcome here. But that makes it all the more important that we take a step back to try to find the truth. From her conclusion:

The timeline of this massive quantity of research and the persistent campaigning of a few early researchers suggest either a brilliant discovery (supine sleep) that was subsequently and resoundingly corroborated by hundreds of studies, or a groundswell of professional opinion that nudged all subsequent research to agree with growing public policy.

Or perhaps more likely, something in the middle: supine sleep has a small effect on SIDS for some, or a large effect for a few, but it may be unnecessary for the vast majority of healthy full-term infants (holding all other risk factors equal), while research has tended to exaggerate the benefit.

*****Update added 9/11/2024*****

Ms. Fama made a fifth post with concluding remarks. Among them was this brief summary:

Should you put your baby to sleep on her back or her belly? I wish I could give you an answer. After my deep dive, I’ve found nothing that proved to me that tummy sleeping by itself is unsafe.