Does bed-sharing with infants increase their risk of SIDS, even without known risk factors such as alcohol use, smoking, and co-sleeping on a couch or chair? A recent study makes what is probably the best attempt to date to answer this question. The study, led by U.K. researcher Peter Blair, was published last week in the journal PLOS ONE and is freely available to the public (yay!).1

Many studies have found that co-sleeping is associated with an increased risk of SIDS, but most of this risk doesn’t come from co-sleeping per se, but rather doing so in particularly hazardous conditions, such as on a couch or with a parent who has been drinking. However, there’s an important, albeit controversial, caveat to this conclusion. Several studies have looked specifically at infants younger than 3 months and still found a significant risk of bed-sharing even in the absence of these other risk factors.2–6 The current study comes to conclusions much more reassuring to bed-sharing parents. In this study, bed-sharing without alcohol, smoking, or couch/chair co-sleeping was not associated with a significant SIDS risk in infants younger than 3 months and even seemed to be protective in older babies. Both of these findings run counter to previous studies and to the sleep recommendations of the AAP, so they deserve a close look.

How was the study conducted?

The study is actually a reanalysis of two previous studies done by the same researchers.7,8 These were case control studies, a type of observational study and the main tool used by researchers to study SIDS risk factors. Combining both data sets together gave the current study a sample size of 400 SIDS infant and 1386 controls.

These studies tracked every sudden unexpected infant death in a defined region (5 regions in the U.K.) for defined periods of time (1993-1996 and 2003-2006). If a death was determined to be SIDS, not due to an identified cause such as a medical condition or suffocation, it was included in the analysis. The families of every SIDS baby were visited within a couple of days of the baby’s death to answer questions about the conditions around the baby’s death, with a follow-up questionnaire scheduled a couple of weeks later. Meanwhile, for each SIDS baby, 4 healthy control babies of the same age and in the same region were recruited, and the control families completed the same interview about how their baby was sleeping at the time the SIDS baby had died. The sleep conditions between the SIDS babies and control babies were then compared to determine significant risk factors for SIDS deaths.

For example, if more of the SIDS babies than the control babies were from households with smokers, then we could conclude that there is an association between smoking and SIDS. In a case control study, this is expressed as an odds ratio (OR), where an OR of 1 indicates no association, OR greater than 1 indicates increased risk, and OR less than 1 indicates decreased risk. Odds ratios are reported with 95% confidence intervals (CI) which tells us how certain we are about this estimate. A very large CI indicates more uncertainty, and if the CI intersects with 1.0 and the P-value is greater than 0.05, then the association is not considered significant.)

It’s always important to keep in mind that a case control study can’t determine that any one factor causes SIDS; it can only establish a correlation. However, for a number of reasons, we can’t do something like a randomized controlled trial for SIDS, so the case control study design is really the best tool we have for looking at SIDS risk factors.

What did the study find?

Like most case control studies of SIDS, this most recent study found that babies that died of SIDS were more likely to be co-sleeping with an adult than to be sleeping alone. However, where the co-sleeping occurred and who was sleeping with baby made a big difference to the risk. For example, co-sleeping on a sofa or chair and bed-sharing with an adult who had more than two alcoholic drinks both increased the odds of dying of SIDS by 18-fold. Bed-sharing with an adult who was a smoker increased the odds by 4-fold. In the absence of these three risk factors, bed-sharing was not associated with increased SIDS risk in this study.

Next, the researchers did an age-based analysis to look at these same risk factors in babies younger than 3 months and older than 3 months. I’ve shown these results in the figure below (created from Table 3 of the paper).

In the figure, note that all of the co-sleeping situations were compared to babies that slept alone, which were automatically given an OR of 1. From there, any higher OR indicates greater risk. This is really evident for co-sleeping on a couch or chair, alcohol use, and in young babies, smoking.

In younger infants, there was not a significant risk of bed-sharing in the absence of the other 3 risk factors. However, the OR for bed-sharing in this group was 1.62 (95% CI of 0.96-2.73; p=0.07). Some might call this a marginal risk for bed-sharing, and since at least 5 other studies have found a risk of bed-sharing with young infants, I would be cautious in assuming this is the final word on this question. However, the data are certainly reassuring. Even if there is a small increased risk in young infants, that risk could easily be trumped by the risk of something like driving with severe sleep deprivation if bed-sharing is the only way you get any sleep.

In older infants, bed-sharing in the absence of the other risk factors actually appears to be protective. (This is hard to see in the figure, but the paper reports an OR of 0.08 for bed-sharing in this group. Only one (0.6%) SIDS infant was bed-sharing with not other risks at the time of death compared with 61 (8.5%) of control infants.) This is a tiny sample, so I think we have to be careful about getting too excited about this result, as we’d like to see it replicated in additional studies. But still, it’s interesting and definitely worth more research.

What does this study mean to parents and policy-makers?

In the SIDS research world, the question of bed-sharing safety is hotly debated. Last year, a study led by Bob Carpenter, another U.K. researcher, looked at similar questions and came to very different conclusions.4 That study found that in babies younger than 3 months, bed-sharing increased the odds of SIDS by 5-fold, even in breastfed babies with nonsmoking parents. The study got lots of media attention and was praised by some SIDS researchers but criticized by others. Among its most vocal critics was Peter Blair, author of the current study. Blair was a peer reviewer for the paper and voiced several major objections [PDF], but presumably since the paper had 3 other very positive reviews, it was still published.9 Perhaps his current study was an attempt to fill in the gaps he saw in Carpenter’s study. In our interpretation of this study, we have to remember that it is just ONE study among many, and in science, we have a responsibility to look at ALL the evidence, not just the study that tells us what we want to hear. Still, this new study was careful and well-designed, and it calls into question some of what we’ve been told about the dangers of bed-sharing.

Policy-makers, such as the AAP’s Task Force on SIDS, are faced with trying to translate this contentious area of research to the public. The AAP’s policy is conservative, recommending room-sharing without bed-sharing and stating, “The AAP does not recommend any specific bed-sharing situations as safe.”10 The policy statement goes on to list specific situations where bed-sharing is especially unsafe (such as with babies younger than 3 months, with a smoker, with an adult under the influence of alcohol, drugs, or medications, on a very soft surface with bedding, etc.). However, the overall message is that your baby should sleep alone in a crib, and this is the message that is emphasized in public health campaigns in the U.S.

The problem with the AAP’s policy is that it doesn’t fully convey the vast differences between co-sleeping in hazardous circumstances, such as on a couch or with an impaired adult, and careful and intentional bed-sharing. We’ve also had pretty good evidence for a while that bed-sharing with infants older than 3 months without smoking or alcohol is not dangerous, but this is glossed over in the AAP statement. And now we have some evidence that it may even be safe to bed-share with younger infants, provided we do it carefully. It may be time for the AAP to rethink their approach to safe sleep recommendations.

We also have to recognize that moms have always and will always sleep with their babies, and no official policy or set of guidelines will change that. Sometimes it is the only way anyone gets any sleep. Sometimes it helps moms keep breastfeeding. Sometimes it just feels right. (Not always, but sometimes.) Parents who choose to bed-share shouldn’t feel like they have to hide this fact from their pediatrician. Instead, they should be having an open conversation about how to make their baby’s sleep environment – crib or shared bed – as safe as possible. And judging from the data in this latest study, the most important points to emphasize to parents are these:

Don’t co-sleep on a couch or chair. If you feed your baby on a couch or chair during the night, and you think there is a chance that you’ll fall asleep there, you’ll probably actually be safer – not to mention more comfortable – feeding in bed. Don’t bed-share if either parent in the bed has had more than 2 drinks of alcohol. (And as a side note, babies should only bed-share with their parents, not kids, pets, or other adults.) Don’t bed-share if either parent smokes, especially with babies younger than 3 months.

The authors of the study write:

“An important implication of our findings is that to give blanket advice to all parents never to bed-share with their infant does not reflect the evidence. There is a danger that such advice could influence parents to seek alternative, more dangerous sleep surfaces such as a sofa. In our study in 2003-2006 a number of families whose infants died informed us that they had been advised not to bed-share and thus fed the infant (and fell asleep) on a sofa… Of course we should inform the public about risks that can be associated with bed-sharing, but bed-sharing is a widespread socio and cultural norm; giving across the board advice to simply not do it negates the option of highlighting the specific and highly significant risks we have found.”

This is a very important study, and I’m glad to see it published. It asks a question that is important to parents trying to figure out how to get a decent and safe night’s sleep. The findings provide guidance on the most important risk factors for SIDS and reassurance to parents who choose to bed-share that these steps can vastly reduce the risk.

What’s most puzzling to me about this study is that it hasn’t gotten more media attention. It’s been available online for a week now, and I haven’t seen a single news article or blog post about it. I honestly can’t figure that one out.

For more information about how to make your baby’s sleep environment as safe as possible, check out Caring for Your Baby At Night from UNICEF UK. This is both evidence-based and practical and is one of the best resources I have found on the topic.

References:

Blair, P. S., Sidebotham, P., Pease, A. & Fleming, P. J. Bed-Sharing in the Absence of Hazardous Circumstances: Is There a Risk of Sudden Infant Death Syndrome? An Analysis from Two Case-Control Studies Conducted in the UK. PLoS ONE 9, e107799 (2014). Blair, P. S. et al. Babies sleeping with parents: case-control study of factors influencing the risk of the sudden infant death syndrome. Br. Med. J. 319, 1457–1462 (1999). Carpenter, R. G. et al. Sudden unexplained infant death in 20 regions in Europe: case control study. Lancet 363, 185–191 (2004). Carpenter, R. et al. Bed sharing when parents do not smoke: is there a risk of SIDS? An individual level analysis of five major case–control studies. BMJ Open 3, (2013). McGarvey, C., McDonnell, M., Hamilton, K., O’Regan, M. & Matthews, T. An 8 year study of risk factors for SIDS: bed-sharing versus non-bed-sharing. Arch. Dis. Child. 91, 318–323 (2006). Tappin, D., Ecob, R. & Brooke, H. Bedsharing, Roomsharing, and Sudden Infant Death Syndrome in Scotland: A Case-control Study. J. Pediatr. 147, 32–37 (2005). Blair, P. S. et al. Hazardous cosleeping environments and risk factors amenable to change: case-control study of SIDS in south west England. Br. Med. J. 339, b3666–b3666 (2009). Fleming, P. J. et al. Environment of infants during sleep and risk of the sudden infant death syndrome: results of 1993-5 case-control study for confidential inquiry into stillbirths and deaths in infancy. Br. Med. J. 313, 191–195 (1996). Horne, R. S., Moon, R. Y., Blair, P. S. & Gilbert, R. Peer Review History for: Bed sharing when parents do not smoke: is there a risk of SIDS? An individual level analysis of five major case–control studies by Carpenter et al. (2013). at <http://bmjopen.bmj.com/content/3/5/e002299> American Academy of Pediatrics – Task Force on Sudden Infant Death Syndrome. Policy Statement: SIDS and other sleep-related infant deaths: expansion of recommendations for a safe infant sleeping environment. Pediatrics 128, 1030–9 (2011).

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