I looked at the policy statement, and although there are 100+ studies cited (not all on co-sleeping, most are on other SIDS risk factors), the ones that appear to be the cause of this new blanket recommendation against co-sleeping (vs. just recommending against co-sleeping after alcohol use, smoking, etc.) are the following:
Carpenter RG, Irgens LM, Blair PS, et al. Sudden unexplained infant death in 20 regions in Europe: case control study. Lancet. 2004;363: 185–191http://www.prematuros.cl/muertesubit...tesubita11.pdf
Tappin DM, Ecob R, Brooke H. Bedsharing, roomsharing and sudden infant death syndrome in Scotland. A case-control study. J Pediatr. 2005;147:32–37http://www.ncbi.nlm.nih.gov/entrez/q...&dopt=Citation
McGarvey C, McDonnell M, Chong A, O’Regan M, Matthews T. Factors relating to the infant’s last sleep environment in sudden infant death syndrome in the Republic of Ireland. Arch Dis Child. 2003;88: 1058–1064http://adc.bmjjournals.com/cgi/conte...d%3B88/12/1058
Other studies are cited in the policy where controlling for smoking, heavy comforter use, sleeping on sofas, and alcohol consumption (i.e., excluding "bad" cosleeping habits) showed that there was no correlation between co-sleeping in bed and SIDS.
I haven't looked at the design of these three studies to see if there were glaring weaknesses, but it appears the AAP is weighting their results heavily, because as I say, there are other studies with outcomes that conflict with these.
ETA: I looked a little at these studies, and even in these, there is only a small significant correlation between increased risk of SIDS and co-sleeping in the same bed for very young babies
(<8 weeks in the largest study, <14 weeks old and <20 weeks old in the other two studies). In all cases, sleeping in the same room but a different bed (and probably sidecar arrangement, too) seem OK.Bottom line: if you co-sleep responsibly with a baby more than a few months old, and your ped or friends/family tell you about the AAP recommendation, you can tell them that it really is only valid for tiny babies so they need not worry... your baby somehow managed to survive that stage!
(I am not endorsing the policy, just trying to understand its basis and the limitations of the data upon which it is based.)