Sleep is one of many physiologic functions that operates in a circadian rhythm, triggered by light–dark changes in the 24-hour cycle. Fatigue is the feeling of tiredness and decreased energy that results from inadequate sleep time or poor quality of sleep. Fatigue can also result from increased work intensity or long work hours. Sleep deprivation has long been known to impair various cognitive functions, including mood, motivation, response time, and initiative. The need for sleep varies individually. The absolute amount of sleep required per 24 hours is generally understood to be a minimum of 5 hours. Most healthy adults need between 7.5–8.5 hours of sleep per night and will experience deficits in cognitive performance when acutely or chronically sleep deprived.
At least two components regulate human sleep: the drive to sleep and circadian wakefulness. The physiologic drive for sleep increases with time awake and decreases during time asleep. As awake time surpasses 12–16 consecutive hours, the drive for sleep becomes increasingly powerful. Wakefulness, like sleep, also has a circadian rhythm: it is highest in the late afternoon and lowest in the early morning hours. Indeed, the strength of the circadian cycle has led researchers to argue that human beings are "biologically hard-wired to be active during the day and sleepy at night. Working at night must therefore be regarded as an inherently unnatural act." (Monk TH. Shiftwork: basic principles. In Kryger MH, Roth T, Dement WC, eds. Principles and Practice of Sleep Medicine. 4th ed. Philadelphia, PA: Elsevier; 2005:673-679.)
Given the importance of sleep and its known effect on cognitive performance, the link between sleep and patient safety has garnered considerable attention. In 2006, AHRQ funded the National Academy of Medicine to synthesize evidence on medical resident schedules and health care safety as well as to recommend strategies to enable optimization of work schedules and patient safety. In this report, fatigue is characterized as a latent hazard and "an unsafe condition" in health care that leads to increased medical error rates. In a classic review of sleep deprivation and decision-making, investigators argued that effective performance in health care environments requires naturalistic decision-making and situation awareness. This type of thinking involves assessing and planning for rapidly changing situations, forming mental models and future status projections, evaluating risks, appreciating the consequences of actions, and rapidly revising plans in light of changing information. These cognitive activities place significant loads on prefrontal cortex functions, such as memory and tracking capacity, which are particularly sensitive to sleep deprivation and related fatigue. Both acute and chronic sleep deprivation result in cumulative deficits in executive function and mood, as well as heightened irritability—and all of these can impair communication and coordination in health care teams. Chronic sleep deprivation can also contribute to burnout, which is increasingly recognized as a threat to patient safety.
In contrast to dynamic, naturalistic decision-making, certain types of cognitive performance are less sensitive to sleep deprivation. Complex tasks that are rule-based and interesting or require critical reasoning in logical well-practiced tasks show less sleep-related degradation of performance. Thus in the context of acute sleep deprivation, individuals may be better able to compensate for cognitive impairment when tasks are complex and interesting (e.g., performing surgery). On the other hand, they may be more susceptible when tasks are rote or rely primarily on vigilance (such as reviewing laboratory tests or ordering medications). This difference may explain why evidence on the effects of acute sleep deprivation (e.g., one night of call) on physician performance has been mixed, despite robust evidence of negative impacts of sleep deprivation and extended work hours in other industries and other aspects of health care.
The effects of sleep deprivation will become increasingly important as health care moves to more shift-based physician staffing. Up to 75% of shift workers experience some degree of fatigue and sleepiness while on duty. There is good evidence of increased nursing errors when shifts last longer than 12 hours, nurses work overtime, or nurses do not receive adequate rest breaks. Similarly, in a classic study of resident work hours, Landrigan and colleagues found medical and diagnostic error were significantly more common in residents working traditional long shifts of more than 24 hours. Studies—including research supported by AHRQ—have shown that residents make fewer errors in the setting of closely monitored, comprehensive interventions to reduce work hours and improve sleep.
Despite ongoing controversies regarding the impact of resident work hour restrictions and physician sleep deprivation on surgical outcomes, The Joint Commission has issued several reports alerting health care providers and the public to the potential for serious adverse effects of lack of sleep. In a 2011 Sentinel Event Alert, The Joint Commission called on health care organizations to take steps to mitigate the impact of extended work hours on clinician sleep deprivation and fatigue. These steps include conducting a risk assessment; ensuring robust handoff practices; involving staff in design of work schedules; implementing a fatigue management plan including strategic use of caffeine and planned naps; educating personnel about sleep hygiene; and ensuring an adequate environment for sleep breaks. However, more evidence is needed to determine optimal practices for scheduling, planned napping, and other fatigue mitigation strategies. The AGCME revised its work hour standards in 2017 to provide more flexibility to physician learners and training programs. Trials are underway to build more evidence for the effect of physician learner work schedules on patient outcomes. One challenge in addressing sleep deprivation among clinicians is that adequate sleep time requires a combination of effective organizational policies regarding work hours, shift rotation, and sleep policies, as well as personal commitment to good sleep habits. Work hour restrictions alone will be ineffective if, when working nights, clinicians do not also limit daytime activities in order to obtain adequate sleep.