Relationship between morningness-eveningness typology and cumulative fatigue or depression among Japanese male workers.

This study clarified relationships between morningness-eveningness typology and cumulative fatigue or depressive state in Japanese male workers. 959 male chemical factory workers answered a questionnaire that included the MEQ, SDS, CFSI, age, marital status, sleep indexes, life habits, and labor load. Logistic regression analysis was performed with SDS and CFSI as objective variables. We obtained valid responses from 884 subjects, who were classified according to MEQ into definitely morning type (4.1%), moderately morning type (38.6%), intermediate type (55.1%), moderately evening type (2.3%), and definitely evening type (0%). The results of logistic regression analysis show that the odds ratio of a subscale among CFSI, chronic fatigue in the moderately evening type (3.33, p=0.046) was elevated compared with that in the intermediate type (2.07, p=0.004). However, the odds ratio of SDS (1.67, p=0.028) and two subscales among CFSI, decreased vitality (1.67, p=0.021), and depressive feelings (2.02, p=0.001), for which significant relationships were found only in the intermediate type, were higher in the moderately evening type than in the intermediate type. These results suggest that relationships between cumulative fatigue or depressive state and circadian typology exist among workers independent of working hours, sleep indexes, or life habits.