The LT evidence base seems pretty clear about the strength of the evidence, although I can see that room sharing isn't the most important factor in preventing SIDS. It says:
"2.1 Room sharing
There is evidence that when infants are placed in the same room as their parents, but they do not share the same sleep surface (i.e. room-sharing not bed-sharing), a significant decrease in the risk of SIDS is seen.96,114 A large study combining case-control studies from 20 regions across Europe showed the risks of SIDS in multivariate ORs of 0.48 (95% CI 0.34-0.69) and 0.32 (95% CI 0.19-0.55) when a room was usually shared and when a room was shared in the last sleep, respectively.96
Babies should sleep in the same room as their parents during the day as well as night. One case control study found that the risk of unsupervised sleep during the day was almost double that of unsupervised sleep at night (adjusted OR for daytime sleep 10.57, 95% CI 1.47-75.96 vs nighttime sleep 5.38, 95% CI 2.67-10.85).64 A travel cot, Moses basket, playpen, or carrycot is suitable for daytime sleep provided other safer sleep advice is followed."
I will admit I haven't read the studies referred to here, but I can see they were published in the Lancet, the BMJ and the International Journal of Epidemiology, so I would assume they are good quality studies. Is that wrong?
I can't really see why the Lullaby Trust and NHS would recommend room sharing if it doesn't actually help decrease SIDS rates. What agenda would they have?
I'm not a medical expert and I'll admit I didn't follow these guidelines to a T anyway, especially with my second baby, who I did leave in his cot with a monitor sometimes from 3 or 4 months. So I'm just curious.