Association does not prove causality

I would like to briefly comment on the article entitled “Prehospital endotracheal intubation in adult major trauma patients with head injury” by Ayan Sen and Raj Nichani.¹ In this excellent review, the authors point out that there are no prospective trials that have investigated the prehospital use of endotracheal intubation in adults. I believe it should be stressed that it is very difficult to account for all confounders using a retrospective design. It is extremely likely that the “sicker” patients were the ones who were intubated in the prehospital setting and therefore had worse outcomes. Until a prospective study is performed, I believe it is quite dangerous to jump to the conclusion that this association proves causality.