The Japanese study reveals the importance of the new

Doctors are a vital part of the medical landscape and, together with other medical professionals, ensure the timely diagnosis, treatment and management of complex diseases. They regularly work extended shifts and overnights, often at the cost of sleep. However, doctors’ long duty hours can lead to physical and mental exhaustion, leading to negative consequences such as depression and burnout. Consequently, this can affect their level of alertness and therefore the quality of patient care. To protect the health of Japanese doctors, a duty hours reform took effect in 2024, limiting overtime to 960 hours annually, with exceptions for doctors serving rural areas and medical interns, whose overtime was capped at 1,860 hours annually.

Although several studies have explored the correlation between working hours and sleep in physicians in general, studies investigating the effects of long working hours on sleep duration and alertness in Japanese physicians are rare. To address this research gap and investigate the benefits of newly implemented overtime limits, a team of scientists conducted a nationwide survey to assess the link between sleep duration, alertness, and psychological health in 1,226 Japanese physicians. The research group consisted of Professor Hiroo Wada and Professor Takeshi Tanigawa from Juntendo University Graduate School of Medicine, Japan, together with Dr Mathias Basner, David Dinges and Makayla Cordoza from the University of Pennsylvania Perelman School of Medicine, USA.

They used standardized surveys to assess physician sleep duration as well as symptoms of burnout (Maslach Burnout Inventory) and depression (Center for Epidemiologic Studies Depression Scale). A brief psychomotor alertness test (PVT-B) was used to objectively assess physician alertness. The results of their research were published in Journal of Sleep Research, on August 12, 2024.

Explaining the motivation behind the present research, Dr. Wada says: “We believe the PVT is a key tool to objectively assess the vigilance levels of essential workers, because self-reported alertness is inaccurate in identifying those with sleep debt, as shown in one of our previous studies. To establish an objective means of assessing vigilance and its links to mental and physical health in physicians working long hours, we collaborated with the University of Pennsylvania, where the PVT was originally developed.

The researchers found that daily sleep duration was inversely related to weekly work hours, and slower PVT responses were significantly associated with both short and long sleep duration. Furthermore, they found that working overtime was linked to increased burnout severity and higher odds of being involved in an accident. Notably, PVT attentional impairments were also associated with increased depression and intense feelings of exhaustion. These findings suggest that PVT performance may be a useful marker of psychological health, but future studies will need to corroborate this finding.

“The stricter 960-hour annual cap on overtime is likely to benefit Japanese doctor’s sleep and mental health. Future studies will need to show whether the suggested limit will be able to meaningfully reduce overtime and improve sleep, alertness and mental health of doctors, or whether an even stricter cap is needed.” says Dr. Basner, a professor in the Department of Psychiatry at the University of Pennsylvania Perelman School of Medicine, who developed the short version of the PVT and has used it in many different populations, including doctors and astronauts in the US.

The present study supports the use of the PVT as an objective assessment tool for physicians’ vigilance, as recommended in the Japanese “Handbook on Health Safety Measures for Physicians Working Long Hours.” Dr. Tanigawa, emphasizing the real-life applications of their research work, adds: “Nearly doubling the cap on overtime for physicians and medical interns serving rural areas may make sense from an administrative perspective, but it doesn’t make sense from a public health and safety perspective. The same cap should apply to all doctors, regardless of the sector they work in or their career progression.”

This research study highlights the importance of adequate rest and adequate sleep duration in maintaining psychological health and alertness levels in physicians. Overall, the study will contribute to a better quality of life for doctors and their patients.

Reference

About Professor Hiroo Wada

Hiroo Wada is a professor in the Department of Public Health, Juntendo University, School of Medicine, Japan. He received his MD and PhD from the University of Tokyo, Japan, and his MBA from Hitotsubashi University, Japan, and completed his graduate studies at Imperial College London, UK. He has been involved in clinical and public health research, focusing on the effect of environmental exposure on health, ie investigating chronic obstructive pulmonary disease and sleep health among children at school and among adults at work. The latter constituted a scientific basis for reforming the working style of doctors. He has published over 110 papers with 1,710 citations.

About Professor Takeshi Tanigawa

Takeshi Tanigawa is Professor at the Department of Public Health, Juntendo University School of Medicine, Japan. His research focuses on epidemiological studies of sleep disorders, cardiovascular diseases and occupational medicine. He received his doctorate from the University of Tokyo in 1990. Over the years, he has published 238 papers and four book chapters that have been cited more than 4,200 times. He is currently the Chair of the Department of Public Health, Juntendo University, and is on the board of various committees and professional bodies.

About Professor Mathias Basner

Dr. Mathias Basner is a professor in the Department of Psychiatry at the University of Pennsylvania Perelman School of Medicine, Philadelphia, USA. His expertise involves sleep and chronobiology, environmental effects on sleep and health, and the behavioral health of astronauts. He received his MD and PhD from the University of Bochum, Germany, and his MSc in Epidemiology from the University of Bielefeld, Germany. He is currently Director of the Behavioral Regulation and Health Section and the Experimental Psychiatry Unit, Division of Sleep and Chronobiology, Department of Psychiatry, University of Pennsylvania Perelman School of Medicine.