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

Abstract

An Occupational Health Study of E m e r g e n c y P h y s i c i a n s i n J a p a n : H e a l t h 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 Bonferroni's 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 0-3 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 physicians' overwork. Overwork would have been a potential risk for the physicians' 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. (J Occup Health 2008; 50: 136-146)

Shift work and cardiovascular disease – pathways from circadian stress to morbidity

“…In addition, 3-shift work has been associated with reduced T-lymphosyte function (66,67). In more recent studies, NK-cell activity was lower among shift compared to daytime workers; among shift workers, activity was also lower during night as compared to day shifts (68,69).…”

Blood natural killer activity is reduced in men with occupational stress and job insecurity working in a university

“…This investigation demonstrated that occupational stress may increase anxiety, negatively correlated with blood cytotoxic activity. Reduced blood NK activity was observed in Japan in emergency physicians and nurses with increased work load (Morikawa et al 2005;Okamoto et al 2008). On the other hand, blood NK cell cytotoxicity was signiWcantly reduced in unemployed men and women (Cohen et al 2007).…”

Effects of Fatigue on Immune Function in Nurses Performing Shift Work

“…Nakano et al 4) reported that lymphocyte proliferation in shift workers was decreased compared with that of fixed-hour daytime workers in a wholesale market and manufacturing company. Okamoto et al 5) also reported that natural killer (NK) cell activity in rotating shift workers was lower than in workers with fixed daytime schedules in a study of medical doctors. However, these studies utilized cross-sectional designs and a direct, causal relationship between shift work and immune function has not been demonstrated.…”