[Mental health and its related factors among middle-aged male workers: an eighteen-month follow-up study].

Based on a longitudinal questionnaire survey of 11, 121 subjects (males aged 30-59, engaged in various occupations snd firms), this study examined the relationships of the baseline psychosocial work environment and personal health practices to mental disorders which occurred during an 18-month follow-up period.The onset of mental disorders during the follow-up period was assumed to be the time when the subject reported to have received medical treatment for the first time due to mental disorder. The psychosocial factors of the work environment were conceptually constructed from two aspects of working conditions and occupational stress. Working conditions were assessed by actual working hours, frequencies of late night work (10 p.m.-5 a.m.), and role in the organization. Occupational stress was measured by psychological work overload and job characteristics (job demands, decision latitude). Various factors associated with positive health behavior were examined through an index based on six variables, that is, supper time, exercise, smoking, alcohol consumption, sleep and weight. Multiple logistic analysis showed that both psychological work overload and late night work have a significant independent effect on the onset of mental disorders after controlling for other variables.