Does safe bed-sharing increase the risk of SIDS?

Question

We were told just prior to checking out of the hospital that sleeping with the infant, along with side-sleeping and front-sleeping, increases the risk of Sudden Infant Death Syndrome (SIDS).

I was under the impression that safe cosleeping habits were just that, safe.

In general, these safety guidelines include:

• No extra objects in the bed: no pillows, no stuffed animals, no loose blankets
• Sleeping surface is firm
• Parents are not smokers, are not intoxicated, or on any medication that causes drowsiness
• Parents are not obese
• Parents are not sick
• And much more

That is far from a complete list. The two lists I linked to are more comprehensive, but they don't all have the same things.

Have there been any studies about whether safe-practice bed-sharing increases the risk of SIDS? I'm looking for information showing a correlation or causation between best-practice bed-sharing and SIDS risk.

Answer 1

Unfortunately, sleeping anywhere - bed, sofa, floor - with the infant nearby is not recommended.

From the CDC site:

Have the baby share your room, not your bed. Your baby should not sleep in an adult bed, on a couch, or on a chair alone, with you, or with anyone else.

From the AAP:

The AAP recommends the arrangement of room-sharing without bed-sharing, or having the infant sleep in the parents' room but on a separate sleep surface (crib or similar surface) close to [but not attached to] the parents' bed.

Evidence exists that room sharing without bed sharing decreases the risk of SIDS by as much as 50%, is safer than bed-sharing, or solitary sleeping (in a separate room). In addition, this arrangement is most likely to prevent suffocation, etc., which may occur when the infant is sleeping in the adult bed. Room-sharing without bed-sharing gives the parents close proximity making feeding, comforting, and monitoring of the infant easier.

In a study from Scotland focusing on sharing sleep surfaces, of 123 infants who dies of SIDS between May 1996 and Jan 2000, the highest risk was associated with couch-sharing, then bedsharing. The final recommendation was against bed-sharing for infants <11 weeks of age, and sharing a couch for sleep should be strongly discouraged at any age.

In this article promoting safe bedsharing, the author implies that bedsharing decreased SIDS because breastfeeding reduces SIDS, and bedsharing promotes breastfeeding. The fact is that parents get better sleep if they don't have to get up to breastfeed, which is the factor promoting breastfeeding. The benefit of breastfeeding in the reduction of SIDS is independent of sleep surfaces.

I would love to say sharing a bed is fine and good. But I can't, not yet. I successfully breastfed my children without bedsharing, so I know it's possible.

_{SIDS and Other Sleep-Related Infant Deaths: Expansion of Recommendations for a Safe Infant Sleeping Environment: Task Force on Sudden Infant Death Syndrome
Bedsharing, roomsharing, and sudden infant death syndrome in Scotland: a case-control study}

Answer 2

The short answer is yes, there have been studies showing an increased risk for SIDS even when several of the known risk factors are removed from the equation:

Carpenter et al. (2013) "Bed sharing when parents do not smoke: is there a risk of SIDS? An individual level analysis of five major case–control studies" Key findings:

When the baby is breastfed and under 3 months, there is a fivefold increase in the risk of SIDS when bed sharing with non-smoking parents and the mother has not taken alcohol or drugs.

Smoking, alcohol and drugs greatly increase the risk associated with bed sharing.

A substantial reduction in SIDS rates could be achieved if parents avoided bed sharing.

In other words, they found that bedsharing was associated with an increased risk of SIDS, even when parents didn't smoke or use drugs and the infant was breastfed. The authors acknowledge that they couldn't control for everything, though, and some of the data they used was missing key questions (e.g. some of the studies included didn't ask mothers about whether or not the smoked or used drugs).

A couple things to keep in mind:

• Research on this topic is tricky because SIDS is not very common. If you start getting very specific about circumstance (infant attributes like pre-term vs. full-term, parent attributes like smoking or drug and alcohol use habits, breastfeeding, bed arrangement, room temperature, etc.), there may only be a handful of cases of infants who have died of SIDS --- not enough to be able to tell statistically whether the risk is increased or not for each subtle change in circumstance.
• Official guidelines are not evidence --- they're recommendations. Because of the limited evidence, recommendations for parents are generally on the conservative side. There is a clear association between bedsharing and increased SIDS risk, and it's not clear whether that's due only to "incorrect" bedsharing practices, so the official recommendations are to not bedshare at all. That doesn't mean it's categorically unsafe to share a bed with your infant, just that the experts don't feel like they have enough evidence to tell you that it is safe.
• Many of the studies on this topic are about identifying risk factors for SIDS, such as parent smoking, soft bedding accessories like as pillows or blankets, sleeping on a couch or armchair, etc. There are well-established links between each of these factors and an increased risk of SIDS. That doesn't mean that avoiding those factors completely reduces the risk of SIDS --- SIDS is still not well understood, and there are certainly risk factors that haven't yet been identified. Pay careful attention to the wording in the sources you read --- no one can promise a way to sleep that will make an infant's chance of SIDS 0%. Avoiding known risk factors may make bedsharing safer, but not necessarily safe.
• SIDS is not the only risk for otherwise healthy infants. Suffocation is an additional risk of bedsharing. Many of the recommendations about how to properly share a bed with an infant (or recommendations to not bedshare at all) are about reducing the risk of nighttime risk in general, not SIDS per se. Some of the studies on this topic lump together all causes of sleep-related infant death, which generally includes SIDS as well as suffocation and strangulation, making it harder to tell what exactly increases the risk for each. If you want a handy summary of evidence on a wide range of sleep-related risk factors for infant death, see the evidence listed in the American Academy of Pediatrics safe sleep guidelines.
• Bedsharing is quite common outside of a modern, US context. That doesn't necessarily mean it's safe, but it does provide some valuable context for US parents who feel overwhelmed by the heated rhetoric on both sides of the debate here.

Answer 3

Firstly, there is a distinction that should be made. Co-sleeping is actually the practice of sleeping in the same room with the baby. Bed-sharing is when the baby sleeps in bed next to or between the parents.

Insofar as any studies go, they can't seem to differentiate between sleep-related deaths or suffocation and SIDS/SUID. IMO, the hospital is full of it. This site gives the following reasons NOT to bed-share

Factors that can increase this risk include:

• a baby sleeping on a couch alone or with a parent
• a baby sleeping between two parents
• a mother who smokes
• parents who are extremely tired
• a parent who has recently used alcohol or drugs
• bed-sharing with pillows or bedcovers

Most of these lend themselves to suffocation in some fashion or another.

This article, done by James McKenna and backed by Meredith Small in her book, give plenty of research behind the benefits of bed-sharing and co-sleeping. (more explanation of the links to come)

My Experience

We used both tactics for both of our kiddos. We have something called a co-sleeper that sits at bed-height so mom can pull the kiddo into bed with her to nurse, then set the kiddo back in the co-sleeper to sleep... all so she doesn't have to get out of bed.

After reading up a bit more, this practice seems to be "acceptable" as far as safe sleeping habits and SIDS are concerned.

Answer 4

There's an important datapoint from Japan which is a developed country where cosleeping is very common. A paper titled Infant Suffocation Incidents Related to Co-Sleeping or Breastfeeding in the Side-Lying Position in Japan explores this subject by first distributing a survey among mothers of infants:

The percent of infants sharing bedding with parents increased significantly with age: 44.9% at 1 month; 56.3% at 4 months; and 76.2% at 10 months. In response to the question of whether co-sleeping or breastfeeding in the side-lying position was practiced regularly, 15.7% of the mothers responded as neither, 28.3% as co-sleeping only, and 56.0% as breastfeeding in the side-lying position. On examining the data based on infant age, 71.3% of mothers of 10-month-old infants were breastfeeding in the side-lying position, which was significantly higher than that for mothers of 1- and 4-month-old infants.

So around 45% of Japanese mothers sleep with babies as young as 1 month old, increasing to 76% by the age of 10 months, which is exactly the dangerous age range according to the CDC. Next they discuss ASSB which a subtype of SIDS:

The incidence of infant ASSB in Japan was 2.5 per 100,000 births in 2016 (Ministry of Internal Affairs and Communications Statistics Bureau 2016). Rates in other countries, such as, 23.0 in the United States in 2015 (Lambert et al. 2018) and 29.0 in New Zealand (The New Zealand Motality Review Group 2016), were higher than the rate in Japan, while the 1.9 in Canada (Gilbert et al. 2012) was similar to Japan. The incidence of ASSB in Japan is lower than in other countries, despite the fact, that co-sleeping is commonly practiced. We believe that this may be attributed to the use of wide and relatively hard bedding (futon) used in Japan. With traditional Japanese bedding, mothers rarely place themselves over infants, while co-sleeping is often performed in a sofa or soft bedding in other countries (Tackett et al. 2010).

So it seems like cosleeping could be very safe if you choose the right sleeping surface. The criteria mentioned in your question similarly refer to hard surfaces being safer. Couches are singled out as particularly unsafe, probably because they're both soft and narrow which is the opposite of Japanese futons which are wide and hard.

It should also be pointed out that Japan has some of the lowest infant mortality rates in the world, so this cannot be attributed to them miscounting SIDS deaths. Finally, remember that preventable SIDS is not particularly common in the first place: CDC statistics show that it went down from 154/100k to 90/100k over 30 years due to various SIDS prevention campaigns. This represents going from a 0.154% chance of a baby dying from SIDS to a 0.09% chance, with a delta of 0.06%. I'll leave it up to each parent to decide if a 0.06% reduction in mortality is important to them.