Effort-reward imbalance and depression in Japanese medical residents.

The effort-reward imbalance is an important psychosocial factor which is related to poor health among employees. However, there are few studies that have evaluated effort-reward imbalance among medical residents. The present study was done to determine the association between psychosocial factors at work as defined by the effort-reward imbalance model and depression among Japanese medical residents. We distributed a questionnaire to 227 medical residents at 16 teaching hospitals in Japan at the end of August 2005. We asked participants to answer questions which included demographic information, depressive symptoms, effort-reward imbalance, over-commitment and social support. Depression was evaluated using the Japanese version of the Center for Epidemiologic Studies-Depression (CES-D) scale. The effort-reward imbalance and over-commitment were assessed by the Effort-Reward Imbalance (ERI) questionnaire which Siegrist developed. Social support was determined on a visual analog scale. Logistic regression analysis was performed to determine the associations between effort-reward imbalance and depressive symptoms. Depressive symptoms were found in 35 (29.2%) 1st-year residents and 21 (27.6%) 2nd-year residents. The effort-reward ratio >1 (OR, 8.83; 95% CI, 2.87-27.12) and low social support score (OR, 2.77, 95% CI, 1.36-5.64) were associated with depressive symptoms among medical residents. Effort-reward imbalance was independently related to depression among Japanese medical residents. The present study suggests that balancing between effort and reward at work is important for medical residents' mental health.

Development of Japanese version of the checklist individual strength questionnaire in a working population.

The aims of the present study were to develop and validate the Japanese version of the checklist individual strength questionnaire (CIS) which is used to measure prolonged fatigue not only in the general population but also in the working population. We obtained permission to use CIS from its author and translated the questionnaire into Japanese. Then, the Japanese version of the questionnaire was translated back into English by a bilingual person. The author of the original version agreed that the back-translated version was conceptually and linguistically equivalent to the original CIS. To validate CIS, 399 workers (66.7% were men) from different companies answered the Japanese version of the CIS (CIS-J), Maslach burnout inventory-general survey (MBI-GS), Beck Depression Inventory-II (BDI-II), visual analogue scale (VAS) questionnaires for subjective fatigue, number of overtime hours and number of hours of sleep. Cronbach's alpha for the total CIS-J score was 0.91. The test-retest reliability assessed with an intra-class correlation coefficient was 0.82. Although confirmatory factor analysis did not show an ideal model fit, the correlation coefficients between the total CIS score and the MBI-GS exhaustion score, the BDI-II score and the VAS score were 0.58 (p<0.01), 0.66 (p<0.01) and 0.63 (p<0.01), respectively. The less workers slept and the longer they worked, the higher their total CIS score became. CIS-J showed good reliability and acceptable validity in the working population. Thus, it could be useful for studying fatigue among Japanese working populations.

Effects of overtime work on blood pressure and body mass index in Japanese male workers.

BACKGROUND: Effects of overtime work on health is a controversial issue. AIMS: To determine the effects of overtime work on blood pressure and body mass index (BMI) for male workers in Japan. METHODS: Participants were 323 male participants of three companies. Data were collected by occupational physicians at periodic physical examinations and additional examinations. The time courses for the development of definite hypertension and an increase in BMI were recorded. The Kaplan-Meier method was used to estimate the cumulative incidence rates of developing definite hypertension and increasing BMI, and the Cox proportional hazard model was used to determine the adjusted relative hazard of overtime work. RESULTS: The age-adjusted incidence rates of developing definite hypertension and increasing BMI were significantly lower among the participants whose mean overtime was > or =50 h than among those whose mean overtime was <50 h/month (log-rank P < 0.05). The Cox proportional hazard model indicated that those who worked a mean overtime of > or =50 h/month had lower risks of developing definite hypertension (hazard ratio, 0.36; 95% CI, 0.15-0.88; P < 0.05) and increasing their BMI (hazard ratio, 0.44; 95% CI, 0.31-0.63; P < 0.01) after adjusting for age. CONCLUSIONS: The results of this study indicate that workers whose mean overtime was > or =50 h have lower risks of developing definite hypertension and increasing their BMI.