Abstract
Approximately 40% of Japanese physicians report working more than 960 hr of overtime annually, with 10% exceeding 1860 hr. To protect their health, annual overtime limits went into effect in 2024. The objective of this study was to investigate associations of self-reported sleep duration with psychological health and objective alertness. This was a cross-sectional National Survey for The Work Style Reform of Long Working Physicians. Physicians self-reported daily sleep duration, burnout (Abbreviated Maslach Burnout Inventory), depression (Center for Epidemiologic Studies Depression Scale) and traffic accidents. Alertness was then evaluated using the brief Psychomotor Vigilance Test. Of 20,382 physicians invited, 1226 completed the survey and brief Psychomotor Vigilance Test. Daily sleep duration was inversely associated with weekly work hours (β = -5.4; 95% confidence interval -6.8 to -4.0, p < 0.0001). Sleep duration < 6 hr and ≥ 8 hr per day was associated with slower responses on the brief Psychomotor Vigilance Test (adjusted p < 0.05). An additional 10 hr worked per week was associated with a 0.40 point (95% confidence interval 0.08-0.72) increase in burnout severity and a 1.7% (95% confidence interval 0.1-3.3%) increase in odds of reporting a traffic accident. Increased brief Psychomotor Vigilance Test lapses, indicating lower alertness, were associated with worse symptoms of depression (β = 0.23 points; 95% confidence interval 0.14-0.31, p < 0.0001) and burnout (β = 0.25 points; 95% confidence interval 0.13-0.36, p < 0.0001). This study emphasizes the importance of sufficient sleep to maintain alertness, and supports limiting work hours for Japanese physicians to protect psychological health. Performance on the brief Psychomotor Vigilance Test may be a useful indicator of psychological health.