The SIDS issue is very complex. Most causes are never defined and you must remember its an end point rather than a condition, so many things can cause it.
The data is sometimes a bit confusing- as an example babies who have died sleeping with parents. There’s some some evidence to suggest that safe cosleeping practices reduce SIDS but the data lumps babies who died sleeping with parents all together, so you get parents who have taken drugs, been heavily drunk along with people who have tragically fallen asleep on the sofa feeding (and god knows that’s easy to do when you’re shattered) and people who bed share all together.
SIDS will have diverse causes - silent heart defects, infections, respiratory depression, being laid on the front and some of those may or may not interact with parental factors (co -sleeping, alcohol, etc etc.)
I know when I co slept I slept very lightly and was always very aware of the baby. There have been video studies done of mums responding to small changes in temperature by moving closer/apart and responding to breathing. So for example a baby who has had a temporary one off breathing stop - maybe a bf/consleepong Mum would notice. Maybe she wouldn’t. But multiply by a million mums and the difference is small but statistically significant.
The causes are complex and the numbers are small. It’s very difficult to do good research but the factors that have been identified drive health policy: ie back to sleep, fresh mattress, no smoking.
Is there anything in breastmilk itself and alone that could reduce the chances of SIDS?
Well one could argue that a bf baby is 4% less likely (number plucked from thin air as a small but not insignificant influence) to get a respiratory infection. Now if that baby is laid on its front and it’s mum is unaware for some reason maybe it has a higher chance of breathing difficulties.
Or maybe the SIDS cause is a hidden heart defect and nothing anyone did could have helped.
The point I’m trying to make is that its complex the numbers are small, the contribution of BF or not to the individual baby is small (visible on a population level as I’ve said a trillion times.)
People are still berating mums for individual choices when these effects are so small it takes hundreds of thousands of Mum/baby pairs to see. Is bf better? Probably, on a population level. Is it better enough to feel guilty about? No.
Again, big red letters, TINY EFFECTS THAT ARE VISIBLE ONLY IN LAGE EXPERIMENTAL OR OBSERVATIONAL POPULATIONS.