1. Introduction

Doctors are notorious for mood swings, and many specialists have attributed it to irregular sleep instead of stress. The theory is consistent with work showing cognitive and motor deficits with sleep deprivation. Recent studies are finding a reason behind cognitive and functional deficits. They are showing that oxidative DNA damage is increased with sleep deprivation. There’s a recent study in Sleep which examined the effects of 30 hours of sleep deprivation on doctors. They showed that 30 hours of sleep deprivation in doctors showed a significant increase in DNA damage using the single cell gel electrophoresis assay compared to a day when they had normal sleep. There are several types of DNA damage that can occur due to reactive oxygen species (ROS), but the main type of oxidative DNA damage studied is 8-hydroxydeoxyguanosine (8-OHdG). ROS are chemical species with a single unpaired electron, which can cause damage to cell function by changing the structure of proteins, lipids, and nucleic acids. Mitochondria are the main source of ROS, and the brain is especially susceptible to oxidative damage due to its high energy demand. Oxidative DNA damage has been linked to several diseases, such as cancer and neurodegenerative diseases, and several studies have linked them to the process of aging. 8-OHdG can cause transversions, where purine-pyrimidine base changes to another, which can result in mutation. It is base pair specific, and 8-OHdG pairs with adenine instead of cytosine. Sleep deprivation is known to affect cognitive and motor function, and 8-OHdG can affect these functions as well. 8-OHdG is removed from cells by the nucleotide excision repair (NER) system, which affects overall brain function. High levels of 8-OHdG have been seen in neurodegenerative diseases and certain types of cancers, both of which have been linked to sleep deprivation. A study in rats showed that the amount of 8-OHdG in the cerebral cortex was significantly higher in the groups that were deprived of sleep. This was reflected in a decrease in NER activity and increased DNA strand breaks.

1.1. Background

It is known that sleep deprivation and disruption have multiple effects on physiological function, including changes in hormone secretion, immunological function, and metabolic and cardiovascular activity (11). The increasing body of evidence demonstrating the adverse effects of shift work and sleep deprivation on patient safety has led to recent changes in medical training and work hours, aimed at preventing the fatigue-related errors of junior doctors. This has obvious benefits for patient safety, however concerns have been raised that reduced working hours may impact on the quality of medical training and doctors’ preparedness for independent practice (12), as well as minimizing the exposure of trainees to the out-of-hours case mix and the supervision of senior doctors. It is likely that further study on the effects of sleep deprivation and fatigue on the performance and safety of doctors will be required to balance these issues.

Recent studies demonstrate that sleep deprivation and disruption, which are inevitable given the early start times and shift working patterns of the medical profession, have similar effects on performance to alcohol intoxication. Subjects undergoing 24 hours of sustained wakefulness, or those with a blood alcohol level of 0.1% (the legal driving limit in Australia), demonstrate impairment in cognitive and psychomotor function equivalent to that seen in individuals with a blood alcohol level of 0.05% – the legal driving limit in the USA and much of Europe (5, 6). Not surprisingly, medical errors made by doctors who have worked for a long time or who are sleep deprived are of great concern. One quarter of the fatal accidents attributed to sleep deprivation in the US are caused by physicians in their post-call day driving home after a night on call (7). In hospital, sleep-deprived physicians have been seen to make more procedural errors and clinical judgment errors (8-10).

Hospitals are staffed around the clock by shift-working medical practitioners. Thirty percent of all medical trainees suffer from depression during their training, a rate five times higher than that of the general population. This is of great concern, given the well-documented association between depression and medical errors (2-4).

1.2. Purpose of the Study

Drs Shea and Czeisler (Shea et al., 2012, this issue) have carefully documented the adverse effects of intern work schedules that do not provide the recommended 8-hour time in bed/24 hours and 5-night on-duty limit. Avoiding extended work shifts for interns, particularly when they do not provide 10-hour time in bed/24 hours, is important for the health and safety of interns. Although one of the primary goals of the Extended Work Hours and Health in Interns (EWHi) study was to observe the effect of the 2011 ACGME duty hours standards change on the training environment and intern work hours, it was predicted that work schedule limitation would improve intern health. A more recent Institute of Medicine (IOM) report, and a Joint consensus statement from the ACGME, ACCME, AOA, CMSS, and LCME has called for reform in the physician work hour environment to improve safety for patients and their caregivers (Wall et al., 2011). Therefore, it is of utmost importance to understand how work hours limits, particularly those meant to improve safety for patients, affect the health of interns. An examination of differences in biomarkers associated with sleep and cardiovascular-related health between the 2003 and 2011 intern cohorts will provide evidence about which schedule characteristics best promoted intern health. This will answer an important secondary aim for the EWHI study and provide an understanding of how work hours reform is related to intern health. Unfortunately, the group observed a total of only 5 disease endpoints among the 2300 participants. Power was heavily limited by the restricted work hours for interns, and observation of disease in younger populations is inherently difficult due to relatively low baseline incidence rates. However, it is hoped that the EWHI study can contribute to strategies for preventing disease in a generally healthier population of young adults. An understanding of how work schedule characteristics affect intern health can provide data about the benefits of schedule limitations and evidence for enforcement of these limits. Collectively, the EWHI study has observed changes in the intern work hour environment that were predicted to improve safety for patients and their caregivers and demonstrated increased time available for sleep during the work week and reduced sleepiness in interns. The group’s studies have provided a demonstration of the feasibility of reducing extended work hours in a medical training program, and the consequent changes in intern sleep and work schedules provide a natural experiment with which to observe effects of work hours limitations on the health of shift working population.

1.3. Research Questions

What is the relation between sleep quantity and quality, diet, and secondary behavioural variables in RMOs? Are there particular groups of RMOs (e.g. those doing shiftwork, during particular rotations, or aged under 40) who are at higher risk of adverse health effects from sleep deprivation? Does recovery sleep over one or more nights, or the timing of sleep, have a positive impact on health and cognitive performance in RMOs? An additional aim of the study is to determine whether high levels of DNA damage in RMOs is due to increased exposure to DNA-damaging agents (such as various chemicals and radiation). To this end, we compare DNA damage in RMOs and control subjects, and assess whether any DNA damage is associated with increased exposure to chemicals and radiation. In RMOs, we also investigate whether increased DNA damage is associated with specific task exposures, particularly those involving extended work hours and administration of on-call medical care.

2. Sleep Deprivation and its Impact on Doctors

2.1. Definition of Sleep Deprivation

2.2. Prevalence of Sleep Deprivation among Doctors

2.3. Factors Contributing to Sleep Deprivation

3. DNA Damage and its Link to Sleep Deprivation

3.1. Overview of DNA Damage

3.2. Mechanisms of DNA Damage

3.3. Previous Studies on Sleep Deprivation and DNA Damage

4. Health Consequences of Sleep Deprivation in Doctors

4.1. Cognitive Impairment

4.2. Emotional Disturbances

4.3. Increased Risk of Medical Errors

5. Strategies to Improve Sleep Quality for Doctors

5.1. Sleep Hygiene Practices

5.2. Work Schedule Modifications

5.3. Supportive Organizational Policies

6. Recommendations for Further Research

6.1. Investigating Long-term Effects of Sleep Deprivation

6.2. Exploring Interventions to Mitigate Sleep Deprivation

6.3. Examining Sleep Deprivation in Different Medical Specialties

7. Conclusion