Objectives: Mental disorders are increasing and their influence on productivity is a concern in the workplace. However, few studies have investigated depression among blue-collar and white-collar workers in the manufacturing industry. The purpose of this study was to clarify the factors associated with depressive symptoms, focusing on lifestyles and insomnia.
Methods: A self-administered questionnaire survey was conducted of 1,963 workers at an annual health checkup in a manufacturing company. Of the 1,712 respondents (response rate: 87%), 1,258 male worker subjects (blue-collar 674; white-collar 584) were analyzed after excluding those with mental diseases. The questionnaire included items on basic attributes and lifestyle. The Athens Insomnia Scale (AIS) and The Center for Epidemiologic Studies for Depression Scale (CES-D) were used to evaluate insomnia and depressive symptoms.
Results: The incidence of depressive symptoms with CES-D scores of ≥16 was 15.1% in both the blue-collar and the white-collar workers. Insomnia with AIS scores of ≥6 were encountered in 18.8% of the blue-collar workers and 18.3% of the white-collar workers. Multiple logistic regression analyses showed that for the blue-collar workers, depressive symptoms were associated with "AIS scores ≥6" (Odds ratio (OR): 10.93; 95% confidence interval (CI): 6.12-19.15), "not get rid of fatigue with sleep" (OR: 3.36; 95%CI: 1.85-6.09), "skip breakfast over 3 times a week" (OR: 3.10; 95%CI:1.42-6.76), "no family living together" (OR: 2.08; 95%CI: 1.05-4.12), and "commuting time" (OR: 1.01; 95%CI: 1.00-1.02). For the white-collar workers, depressive symptoms were related to "AIS scores ≥6" (OR: 14.91; 95%CI: 7.54-29.49), and "no family living together" (OR: 2.54; 95%CI: 1.27-5.09). Sleep time was not associated with depression in both blue- and white-collar workers. Depressive symptoms were found in 51.6% of the blue-collar workers with insomnia with AIS scores ≥6 and 53.8% of white-collar workers.
Conclusions: Depressive symptoms were found at the same prevalence rate in both blue-collar and white-collar workers, which suggests that health measures for depression are necessary for both types of worker. Depressive symptoms were significantly associated with insomnia. Health advice focusing on insomnia as well as lifestyle may be important for workers.