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J Occup Health year 2008 volume 50 number 2 page 136 - 146
Classification Originals
Title An Occupational Health Study of Emergency Physicians in Japan: Health Assessment by Immune Variables (CD4, CD8, CD56, and NK Cell Activity) at the Beginning of Work
Author Hiroteru Okamoto1, Tooru Tsunoda1, Koji Teruya1, 2, Nobuo Takeda1, Takamoto Uemura1, Tomoko Matsui1, Shinji Fukazawa1, Kaoru Ichikawa1, Rieko Takemae1, Kosuke Tsuchida1 and Yutaka Takashima1
Organization 1Department of Preventive Medicine and Public Health, School of Medicine and 2Department of Public Health, Faculty of Health Sciences, Kyorin University, Japan
Keywords Occupational health, Emergency physicians (EPs), Workload of chronic overwork, Shift work, Natural killer cell (NK cell), CD56, Quality of emergency medical services
Correspondence H. Okamoto, Department of Preventive Medicine and Public Health, School of Medicine, Kyorin University, 6-20-2 Shinkawa, Mitaka-shi, Tokyo 181-8611, Japan (e-mail: hph-okamoto@kyorin-u.ac.jp)
Abstract An Occupational Health Study of Emergency Physicians in Japan: Health Assessment by Immune Variables (CD4, CD8, CD56, and NK cell activity) at the Beginning of Work: Hiroteru Okamoto, et al. Department of Preventive Medicine and Public Health, School of Medicine, Kyorin University-This study was conducted to evaluate the occupational health of Japanese physicians in emergency medicine. Subjects participating in this study were eighty-nine physicians working at 12 medical facilities (10 critical care emergency centers) in Japan. Participants were asked to complete a questionnaire of work conditions and to provide blood samples for immune variable measurements (CD4, CD8, CD56 and natural killer cell (NK cell) activity) before commencing their work. The data collected from seventy-four of 89 participating physicians were analyzed. The traditional work group comprised of 39 emergency physicians, who were significantly overworked compared to other two groups: the shift work group and the day work group. Among these three groups, no immune variable was significantly different except lymphocyte, number of CD4, and NK cell activity; and the NK cell activity of the shift work group was significantly lower than those of the traditional work group (p<0.01) and the day work group (p<0.01) in terms of BonferroniÕs multiple comparison, probably due to circadian rhythm. It was indicated that NK cell activity was significantly lower in samples collected at night versus in the morning (OR=8.34, 95%CI: 1.95-35.6, p<0.01) through multiple logistic regression analyses. NK cell activity was significantly lower in individuals taking 0Š3 days off per month, as compared to those taking 4 or more days off (OR=4.65, 95%CI: 1.27-17.0, p=0.02), according to multiple logistic regression analyses. Therefore, the low NK cell activity appears to have reflected the extent of fatigue arising from physiciansÕ overwork. Overwork would have been a potential risk for the physiciansÕ health, resulting in a lower quality of Japanese emergency medical services than that which could have been achieved otherwise. This study suggests that it would be better for the Japanese emergency physicians to take 4 or more days off per month for their health and the quality of their services.