This is a well-designed study with interesting and important results. I found the results to be very disturbing and believe they deserve public attention. BMJ should publish this article after much needed revisions -- I called them minor revisions but others may disagree. The main problem is that the Discussion section does not discuss the findings, it just repeats the same statistics that were previously presented in the Results section. Instead, it should explain why the results are important, what are the implications for the practice of medicine, public health, public policy, or whatever the authors want to tackle. The Conclusions section also needs to be revised: it is only two sentences, both of which raise issues that don't belong there because they were not raised previously -- and probably should have been discussed in the Discussion section.

This is a well written, important study based on an enormous dataset. As noted in the manuscript, these types of data raise questions that can't be answered, but raising the questions is in itself important. In response to my earlier criticisms, the Discussion section is now very good and the Conclusion section is also improved. I also agree with the changes that the authors made in response to the suggestions of Reviewer #2.