Objective: The purpose of this study was to determine whether leisure time physical activity moderated the relationship between job stress and depressive symptoms among Japanese workers.
Methods: This study was based on cross-sectional survey data collected from 695 men and 134 women（ 40－62 yr, 49.4±6.0 yr） who worked in a precision machine factory. Subjects taking antidepressant drugs were excluded from analysis. Self-report measures of leisure time physical activity （LTPA）, job strain （Job Content Questionnaire; JCQ）, and depressive symptom （Center for Epidemiologic Studies Depression Scale; CES-D） were measured. Depressive symptoms was defi ned as CES-D score ≥ 16 point. “Active group” was defi ned as LTPA ≥ 4 time/mo, and “Sedentary group” was defi ned as LTPA < 4 time/mo. Subjects were categorized in four groups （Low-strain, Active, Passive, and Hi-strain） based on the median score of job demand and job control of JCQ. Odds ratio and 95% confi dence interval（ 95%CI） of depressive symptoms in the joint JCQ group and LTPA group model were calculated using multiple logistic regression analysis, adjusted for potentially confounding factors such as age, sex, marital status, hours of sleep, and overtime work.
Results: The prevalence rate of depressive symptoms was 21.1% in all subjects. In the Sedentary group, the high prevalence of depressive symptoms was observed in the higher job strain group（ Low-strain: 13.5%, Active: 20.8%, Passive: 23.0%, Hi-strain: 37.8%）, but it was not observed in the Active group. Odds ratio of depressive symptoms was higher in the Hi-strain-Sedentary group than the Low-strain-Active group（ 3.27, 95%CI: 1.38－7.70）.
Conclusion: These fi ndings suggest that the depressive symptoms associated with job stress may be reduced by participation in leisure time physical activity. Prospective epidemiological studies and controlled intervention trials are needed to examine the buffering effect of leisure time physical activity on job stress.
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