I believe those cases are included in SIDS statistics. I can’t find it but NPR had a long informative show with a doctor talking about SIDS, she mentioned that if you take out overweight/drunk parents the risk of SIDS from co sleeping is actually very low

EDIT: Another important factor is where the sleeping occurs. A bed is very safe, a couch is not. She pointed out that an exhausted parent lying down with the child for an intentional nap is much better than them falling asleep sitting up on the couch.