We would like to thank Dr Sarani and Dr Alarcon for their critique of our work, published online in Critical Care on 12 January 2005 [1]. We have reviewed the critique, and in general we think that it appropriately describes both the strengths and limitations of our studies.
We would like to make a few minor factual clarifications. First, although the study by Lockley and colleagues used a within-subjects analytical design [2], the study by Landrigan and colleagues did not [3]. A systemic-level approach rather than a within-subjects analysis was used in comparing interns' serious medical error rates, making these analyses comparable with analyses of errors system wide (i.e. those that involved both interns and other personnel), where a within-subjects design was not appropriate. Data from 20 interns were analyzed in Lockley and colleagues' study, as the authors note; however, data from an additional four interns contributed to the analysis in the study by Landrigan and colleagues. Our power to detect a 16% difference in serious medical errors was calculated to be 80%, not 90%. In addition, there is one error in the description of the limitations that we would like to point out. Dr Sarani and Dr Alarcon note:
There were more patients admitted to the ICU and more ICU patient-days in the traditional arm than in the intervention arm. Although these differences were not statistically significant, it does raise the possibility that interns in the traditional arm had more opportunities to make serious errors.
Differences in the incidence of serious errors were analyzed using rates (per patient-day), and therefore the fact that there were more patient-days in the traditional schedule cannot explain the results. On a per patient-day basis, there were no more opportunities to err in the traditional schedule. This is further confirmed by the fact that there were no more medications ordered or diagnostic tests interpreted in the traditional schedule per patient-day, and there were in fact fewer procedures performed in the traditional schedule per patient-day.
With respect to the recommendations following from our findings, we strongly disagree with Dr Sarani and Dr Alarcon's statement that our study supports the Accreditation Council for Graduate Medical Education (ACGME) duty-hour standards:
Based on the results of these studies, it seems that the ACGME resident work hour restrictions are warranted, at least for interns, and that efforts to reduce the number of hours worked by interns may improve patient care.
Although we would agree that efforts to reduce the number of hours worked by interns may improve patient care, our traditional schedule was in fact compliant with the ACGME duty-hour standards. In effect, we were comparing these standards with a schedule that much more substantially reduced continuous working hours than the ACGME regulations demand, with a maximum of 16 scheduled consecutive hours. Our data support an extensive literature, derived from laboratory and field studies in other safety-sensitive industries, that 24 hours or more consecutive work are unsafe. Efforts to reduce work hours should focus first and foremost not on the frequency of extended-duration work shifts, but on the duration of consecutive work hours during such shifts. Research from laboratory and industrial settings suggests that performance deteriorates rapidly and the propensity to err rapidly increases after 16 hours of sustained wakefulness, a finding reflected in the twofold increase in interns' attentional failures after they had been working for more than 16 hours on the traditional schedule [2].
We agree with the recommendation that further research should study the effects of sleep deprivation and work schedule interventions on the performance of upper-level residents and other medical staff across a variety of disciplines. We likewise agree that optimizing patient hand-offs, medical education, and trainees' sense of professionalism should be priorities as interventions are developed that reduce consecutive work hours to ensure the safety of patient care. We believe, however, that development of 'a sense of professionalism' is not a function of whether a shift is 30 hours or is 16 hours, but is a function of the ethical priorities engendered through the medical training process; first among these is the moral obligation to 'Do No Harm'. Carefully controlled studies of our own systems and practices are essential to determine how best to protect patients and, ultimately, the integrity of our profession.
With respect to medical education, it is important to recognize that sleep deprivation has been found to adversely affect education as well as resident and patient safety. Recent work has demonstrated markedly impaired learning among research subjects deprived of sleep [4-6]. Whether residents exposed to recurrent acute sleep deprivation learn more or learn less than better-rested residents who spend fewer hours in the hospital remains to be tested, and should be a major focus of future work.
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