In this issue of JAMA Internal Medicine, a cross-sectional study by Sun et al1 addresses the important question of whether a surgeon operating overnight is associated with worse operative outcomes for surgeries performed the following day. The authors used data from the Multicenter Perioperative Outcomes Group (MPOG) registry, including 498 234 operations performed by 1131 unique surgeons who operate overnight, to demonstrate that after adjusting for confounders, there was no difference in major or minor surgical complications between surgeons who worked the night prior and those who did not.1 Importantly, the study controlled for surgeon fixed effects, by which individual surgeons act as their own control using a surgeon-specific indicator variable, and conducted a subgroup analysis of higher-risk patients and sensitivity analyses for amount of time spent operating the night prior; none of these additional analyses changed the results.