This study was very well designed and the authors took great pains to identify the surgeons with sleep deficits after night work. And I think that the use of billing codes is an extremely creative way to design this study. What are all of your thoughts about the authors' retrospective design and use of billing codes to approximate overnight activity?
And to the authors, Drs. Baxter and Govindarajan, I'd also be curious to find out what other ways you considered to identify the night working surgeons.