Japanese study shows importance of new

Physicians are a vital component of the healthcare system and, along with other healthcare professionals, provide timely diagnosis, treatment and management of complex diseases. They regularly work extended and night shifts, often at the expense of sleep. However, doctors’ long work hours can lead to physical and mental exhaustion, leading to negative consequences such as depression and burnout. Consequently, this may affect their level of attentiveness and therefore the quality of patient care. To protect the health of Japanese doctors, working time reform came into force in 2024, limiting overtime to 960 hours per year, with the exception of doctors who serve rural areas and medical trainees, whose overtime was limited to 1,860 hours per year.

Although several studies have examined the correlation between working hours and sleep in physicians in general, there is a paucity of studies examining the effects of long working hours on sleep duration and alertness in Japanese physicians. To address this research gap and examine the benefits of recently introduced overtime restrictions, a team of researchers conducted a national survey to assess the relationship between sleep duration, alertness, and psychological health among 1,226 Japanese physicians. The research team consisted of Professor Hiroo Wada and Professor Takeshi Tanigawa from Juntendo University Graduate School of Medicine, Japan, as well as Drs. Matthias Basner, David Dinges and Makayla Cordoza from the Perelman School of Medicine, University of Pennsylvania, 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). The Psychomotor Vigilance Test-Brief (PVT-B) was used to objectively assess physician attentiveness. The results of their research were published in the journal Journal of Sleep Research, August 12, 2024

Explaining the motivation for this study, Dr. Wada says: “We believe that PVT is a key tool for objectively assessing the level of alertness of essential workers, as self-reported alertness does not identify individuals with sleep deprivation, as shown in one of our previous studies. To establish an objective means of assessing vigilance and its relationship to the mental and physical health of long-term physicians, 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 responses to PVT were significantly associated with both short and long sleep duration. They also found that working extra hours was associated with increased severity of burnout and increased odds of being involved in an accident. Notably, attention lapses in the PVT were also associated with increased depression and greater feelings of burnout. These results suggest that PVT performance may be a useful indicator of psychological health, but future research should confirm this finding.

“A stricter overtime limit of 960 hours per year is likely to benefit the sleep and mental health of Japanese doctors. Future research will need to show whether the proposed restriction can significantly reduce overtime and improve doctors’ sleep, alertness and mental health, or whether an even more stringent restriction is necessary.” says Dr. Basner, a professor in the department of psychiatry at the Perelman School of Medicine at the University of Pennsylvania, who developed a short version of the PVT and has used it in a wide variety of populations, including American doctors and astronauts.

The present study supports the use of PVT as an objective assessment tool for physician attentiveness, as recommended in the “Guidelines on Health Safety Measures for Physicians Working Overtime” in Japan. Dr. Tanigawa, emphasizing the practical application of their research work, adds: “Nearly doubling the overtime limit for doctors and medical trainees serving rural areas may make sense from an administrative standpoint, but it makes little sense from a public health and safety standpoint. The same limit should apply to all doctors, regardless of the industry they work in or their career path.”

This study highlights the importance of adequate rest and appropriate sleep duration to maintain physicians’ psychological health and activity levels. Overall, the study will help improve the quality of life of doctors and their patients.

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About Professor Hiroo Wada

Hiroo Wada is a Professor in the Department of Public Health, Juntendo University Graduate School of Medicine, Japan. He received his MD and PhD from the University of Tokyo, Japan, and his MBA from Hitotsubashi University, Japan, and continued his higher education at Imperial College London, UK. He has been involved in clinical and public health research on the effects of the environment on health, e.g. studying chronic obstructive pulmonary disease and sleep health among children at school and among adults in the workplace. The latter formed the scientific basis for the reform of the working style of doctors. He has published over 110 papers with 1710 citations.

About Professor Takeshi Tanigawa

Takeshi Tanigawa is a professor in the Department of Public Health at Juntendo University Graduate 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 Graduate School of Medicine in 1990. Over the years, he published 238 articles and four book chapters, which have been cited more than 4,200 times. He is currently the head of the Department of Public Health at Hongtendo University and serves on the boards of various committees and professional organizations.

About Professor Matthias Basner

Dr. Matthias Basner is Professor in the Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, USA. His expertise includes sleep and chronobiology, environmental influences on sleep and health, and astronaut behavioral health. 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 the Director of the Division of Behavioral Regulation and Health and the Division of Experimental Psychiatry in the Division of Sleep and Chronobiology in the Department of Psychiatry at the Perelman School of Medicine at the University of Pennsylvania.