To examine the effect of shiftwork on lifestyle and mental health, a self-administered questionnaire survey was conducted among employees of a leading electrical appliances manufacturing company in Japan. The questionnaire included eight health practices recommended by Morimoto, the General Health Questionnaire-28 (GHQ-28) and demographic variables. Considering the effects of type of occupation, working hours and gender, analysis was focused on 295 male blue-collar mere employees working less than 8 hours per day and engaged in daytime work or two-shift work. Scores for Health Practice Index (HPI) and physical exercise of shift workers were significantly lower than those of daytime workers for those from 30 to 45 years of age (p&lt
0.05). However, in scores for HPI and each lifestyle factor, no significant difference was found among shift workers and daytime workers 29 or younger and 46 and older. In scores for the total GHQ-28 and its four subscales, no significant differences were found among shift workers and daytime workers 29 or younger, between 30 and 45, and 46 years of age and older. No significant effect of shiftwork was found on mental health status and lifestyle practices excluding physical exercise. The findings suggested reduction of physiological and psychological stress due to shiftwork among employees of the major company. However, the effect of shiftwork on lifestyle practices and mental health status might be affected by various factors. Therefore an investigation of the work load in regard to shiftwork should be conducted precisely in the future.