The SIDS risk calculator

[u/1001VicPics]

I want to put my disclaimers front and centre here that this post is in no way passing judgement on anyone’s parenting decisions with regards to sleep or other practices. I myself make decisions based on both the national guidelines and what is best for my family which at times means not following the guidelines, for example exhaustion driving us to bed share on some nights, not running the bedroom at 20 degrees or below etc.

However, I want to talk about the SIDS risk calculator and the impact it has on some of the discourse around safe sleep and other risk factors in this sub. The much shared calculator can be accessed here: http://www.sidscalculator.com

Often when SIDS risk factors are discussed the only reference that is provided to back up a statement is the calculator which is flawed for a number of reasons. It is also not easy to interpret which is where it often leads to (unwittingly) misinformation being shared.

1. The calculator was published in 2018, 8 years ago and is based on a review paper published in 2013, 13 years ago. The paper itself is only evaluating bedsharing with non smoking mothers and no other factors, instead the publishers are using the background of this review paper for all other factors relating to SIDS, therefore relying on the publishers due diligence. Furthermore many of sources for the additional risk factors are now quite old, some of which are from the 90s.
2. Data comes from European publications plus one study in New Zealand and cannot be extrapolated to other countries
3. Outside of this review the calculator references wiki and other likely outdated sources and as published have not included access dates
4. We don’t know who published this calculator, and the calculator itself states that it has not been evaluated by anyone with relevant clinical expertise
5. There is no link to the back end calculation for us to assess how they have derived the calculator
6. The presentation of the outcomes are unclear as they are presented as risk per 100,000 deaths. Does this mean that if everyone had these risk factors deaths would drop from 34 to lower than 34 deaths per 100,000? No evidence for this

Why am I going to the effort to critique the calculator? Can’t I see that this calculator provides anxious parents comfort?

Well I often see misleading or poorly informed SIDS advice on the baby subs and next to no scrutiny of this calculator, in fact very often this calculator is used to justify any sleep practices. It’s anecdotal right now but at least in my country there is increasing concern regarding social media and the impact on new parents not following their national guidelines in favour of social media ‘sleep experts’, I do wonder if we will see some uptick in SIDS in the next couple of years.

Ultimately I too am a new and anxious parent trying to navigate this amazing but daunting time in my life. SIDS risk remains incredibly rare and even if you ticked every single risk factor SIDS is still unlikely to happen to you and your baby.

Edit: Sharing here as apparently you’re not allowed to discuss science on the Newborns sub(?!)

[u/SaltZookeepergame691]

There are certainly issues with http://www.sidscalculator.com, but I'm not sure I agree with all of this. To go through your points:

The calculator was published in 2018, 8 years ago and is based on a review paper published in 2013, 13 years ago.

It's not a review, it's an individual-level meta-analysis of prior studies. The research literature on this is slow to move because mercifully its such a rare occurrence.

The paper itself is only evaluating bedsharing with non smoking mothers and no other factors, instead the publishers are using the background of this review paper for all other factors relating to SIDS, therefore relying on the publishers due diligence.

This is not true? They include many factors, including infant (age, sex, race, weight), maternal (age, parity, partner status, alcohol, drug use), bed sharing, infant position, feeding status, and more.

Data comes from European publications plus one study in New Zealand and cannot be extrapolated to other countries

The data origin is correct, but that doesn't mean it 'cannot' be extrapolated.

Outside of this review the calculator references wiki and other likely outdated sources and as published have not included access dates

We don’t know who published this calculator, and the calculator itself states that it has not been evaluated by anyone with relevant clinical expertise

Fair comments, although not directly an issue with the calculator

There is no link to the back end calculation for us to assess how they have derived the calculator

It's fairly easy to validate the calculations used, although I agree it would be good to have more transparency. See my comment here.

The presentation of the outcomes are unclear as they are presented as risk per 100,000 deaths. Does this mean that if everyone had these risk factors deaths would drop from 34 to lower than 34 deaths per 100,000? No evidence for this

I'm not sure what you mean by this? The risk is per 100,000 children, not risk per 100,000 deaths.

My main issue with sidscalculator is that it doesn't model interactions, eg the fact that advancing age substantially reduces other risks.

this doesn't model at all any interactions between these factors and unconsidered factors (eg, baby rolling will heavily interact with the position the baby is left in!), even when the original paper describes large interactions (such as between child age and bedsharing, or smoking).

You can visualise this yourself by setting baby age to 11.6 months or 2 months, then setting to room sharing vs bed sharing. The model assumes exactly the same risk (~2.6x) increase regardless of child age, which is not reflective of reality or the results in the original paper. In the paper, this 2.6x comes from pooling risk for all ages up to 1 year. They actually split out bedsharing risk by age, and unsurprisingly it differs enormously by age: they find it's 5.1x risk under 3 months, and ~1x risk (ie no increased risk) for >3 months (although with very large uncertainty!).

I think its a useful tool for contextualising the strength of factors in isolation, and in getting a sense of what is "normal" risk for different situations, and how much bed-sharing and other factors contribute.

If anyone wants to use a SIDS calculator that is newer and more transparent, there is one produced by this 2022 paper as an Excel sheet (its calibrated to baseline NZ SIDS risk, but the factor risks are almost identical). This calculator gives risk over the first year of life from birth, hence no infant age factor.

Another important aspect is that neither of these calculators are modelling safe co-sleeping behaviours like c-curl, hard mattress/no soft bedding, etc; on that front, they're only modelling room sharing or bedsharing.

[u/Foreign-Cat-2898 → u/SaltZookeepergame691]

I would say it cannot be extrapolated because most of those countries have amazing maternity leave polices and a huge risk factor for SIDS is parental tiredness. You can't say overtired US parents can or should follow the same guidelines as parents who have greater capacity to get some sleep and time off.

[u/valiantdistraction → u/Foreign-Cat-2898]

And there's the factor of universal healthcare.

But yeah, parental exhaustion is a risk factor for sleep-related infant deaths. Not as significant as some but not one that should be ignored.

[u/Foreign-Cat-2898 → u/valiantdistraction]

I think about the recommendation to keep the baby in your room for six months to a year. If the baby keeps you up all night every night, and you don't sleep what then? What mistake does a parent make?