What is the risk of SIDS for babies which sleep on their stomach (no other risk factors)?

Question

Bear with me, as I'm not very good with statistics. As far as I can tell the risk of SIDS as of 2014 is 1 in 2,500 according to the CDC (obtained by reducing the 38.7 deaths per 100,000 to lowest terms). However, the CDC gives no information about the risk of SIDS for a baby whose parents follow all the recommended guidelines. In other words, the SIDS statistics include parents that smoked and wrapped children in large warm blankets. Is there any information about the risk of SIDS for a child which prone sleeps in a situation with a firm mattress, non-smoking parents, no extra bedding, etc.? It would also be great to know the risk of SIDS for the same baby sleeping on his back too. Please include sources.

The only information I could find on the risks of SIDS without other risk factors is this blog. It states:

Taking this into account, for people who have no other risk factors, here are the new odds (roughly):

— Chances of a prone-sleeping infant succumbing to SIDS with no other risk factors: about 1 in 20,000 (range 10,000–25,000)

— Chances of a supine-sleeping infant succumbing to SIDS with no other risk factors: about 1 in 50,000 (range 25,000–60,000)

(Note — the numbers don’t quite match up with the other statistics quoted above, because the estimates were generated from a few different studies and calculated in a couple different ways.)

However, the author admits that he cannot provide sources but claims that he looked at several medical studies.

Answer 1

I think that the position in that blog is likely to be close to the truth. The dirty little secret is that SIDS is likely most closely related to parental, and in particular maternal, alcoholism and overweight. Alcohol makes it less likely that a parent will wake up in response to sounds of distress from the infant; the mechanism for overweight is less clear, but the correlation exists.

Here's an article showing that diagnosed alcoholism in the mother increases the chance of SIDS by a factor of 7, accounting for at least 16% of SIDS deaths:

http://www.ncbi.nlm.nih.gov/pubmed/23439895

Considering how much alcohol use does not rise to the level of alcoholism, and how much alcoholism is undiagnosed, alcohol accounts for a large chunk of SIDS deaths.

Here is a study saying that maternal overweight and obesity accounts for a 1 in 4000 chance of infant death:

http://www.bmj.com/content/349/bmj.g6572

The study is from Sweden so it didn't use the SIDS classification, but if many of those are SIDS cases, that would account for another big chunk of SIDS deaths, perhaps more than half. U.S. studies have come up with similar risk factors. While being obese only increases the chances of infant death by about a factor of 2, rather than the factor of 7 for alcoholism, obesity is so much more common that it probably accounts for a larger absolute number of deaths.

Note that another risk factor is having the infant sleeping in a different room from the parents, presumably because it's more difficult to hear a distressed infant in a different room.

So, don't drink, control your weight, and have the baby in the same room as you, along with the care you are taking with bedding and such, and you should have covered most of the major bases.

Answer 2

I'm afraid I don't have the exact statistics that you're asking for but here is an interesting article about how the advice to put babies on their backs for sleeping came to be so widely recommended and campaigned for:

https://www.theguardian.com/society/2016/aug/26/back-to-sleep-sudden-infant-death-syndrome-cot-death-peter-fleming

This advice has saved a huge number of lives. According to the article:

"(SIDS) became an epidemic between 1970 and 1991, and, at its peak, babies in some of the world’s richest countries were dying at the rate of one in every 250 live births each year."

Since the campaign to put babies on their backs to sleep, the SIDS death rate in England and Wales in 2013 was one in every 3,000. This particular article doesn't say how many of these 1 in 3000 babies were sleeping on their back or front or have other risk factors but you could make a rough assumption that before the campaign, the majority of babies were put to sleep their tummies as that was the advice and since the campaign, most babies sleep on their backs, resulting in around a ten fold reduction in SIDS deaths.

During the time when this link was discovered between front sleeping and SIDS, the sleeping position was the main thing that was changed, leading to this massive reduction in deaths:

"In December 1991 the Back to Sleep campaign was launched. Sids deaths in the UK fell instantly, and with astonishing speed. In 1989 there were 1,545 Sids deaths. Now there are barely 200 a year."

The 200 a year may be related to other risk factors or parents who are unaware of or don't follow the advice. It seems that however careful you are about the other risk factors, on this basis, the simple advice of having your baby sleep on its back is most likely worth following.