Nighttime physician staffing improves patient outcomes: yes.

Nighttime physician staffing improves patient outcomes. This is supported by the literature [1–5] and we have all seen it personally. The question is really not whether nighttime intensivists improve outcomes, but rather when, where, how and at what cost. The question hinges on context. There is abundant evidence that nighttime physician staffing is responsible for improved patient outcomes both directly and indirectly in a variety of settings. Nighttime physician staffing is associated with improved intensive care unit mortality [1, 3, 5], improved quality of death and dying [2], and alignment of care to patient preferences outside the intensive care unit [4]. Nighttime intensivists improve outcomes for patients with unexpected deterioration after hours, albeit in ways that are difficult to capture in clinical research. Nighttime intensivist staffing also indirectly improves patient care by mitigating the negative effects of cognitive fatigue and sleep deprivation in a daytime-only staffing model [6]. Both cognitive fatigue and sleep deprivation are associated with impaired performance, decreased use of decisional support, compromised patient safety, and physician burnout [7–9]. Nighttime intensivist staffing mitigates some of these effects by allowing the daytime attending to rest at night [6], thereby improving the care that is delivered during the day. Therefore, in the right setting, through both direct impacts on patient care overnight and indirectly by facilitating high quality care during the day, nighttime staffing improves patient outcomes. Context is equally important for reconciling the results of studies that did not find benefits from nighttime physician staffing. A recent randomized trial of nighttime staffing in a large academic medical intensive care unit did not show improved patient survival or length of stay [10]. It is certainly possible (if not likely) that the study’s 1-week cycling of daytime-only staffing was not sufficient to unmask the deleterious effects of cognitive and physical fatigue, contributing to a null result. Similarly, 1-week daytime-only staffing cycles would be unlikely to induce physician burnout or emotional exhaustion—domains related to patient safety in critical care that are improved by nighttime staffing [11, 12]. A closer look at the University of Pennsylvania study demonstrates how, taken out of the context of avoiding physician burnout or alleviating cumulative cognitive and physical fatigue, the study biased the effect of nighttime staffing towards the null. Figure 1 shows that when an effect of accumulating fatigue is included, there are now four exposure categories. In the study’s main analysis, patients A and D were considered equivalent: both were admitted to and analyzed in the intervention arm. Similarly, patients B and C were included as controls. However, as the figure shows, patients A–D represent different admission scenarios. Patient A is admitted on a calendar day with nighttime intensivist staffing, yet the daytime attending is still moderately fresh. In this setting, as it relates to the domain of cumulative cognitive and physical fatigue, we would not expect the nighttime intensivist to have a major impact on daytime care. However, patient D is also admitted to a calendar day with nighttime intensivist staffing, yet here the daytime attending is nearing the end of service, and consequently stands the most to benefit from intensivist staffing at night. A similar situation is present for the controls. Patient B is admitted to a calendar day with only daytime coverage and near the end of service, during the highest risk of cumulative fatigue effects. Patient C is admitted to a calendar day with only daytime coverage, but early in the service cycle, with lower attendant risks from fatigue. Again, in the main analysis, patients A and *Correspondence: wallacedj@upmc.edu Department of Critical Care Medicine, University of Pittsburgh School of Medicine, Pittsburgh, USA