Objectives: We prospectively examined the combined effect of high stress (i.e., being under great work-related stress), as defined in the Japanese Stress Check Program manual using the Brief Job Stress Questionnaire (BJSQ), and job dissatisfaction on long-term sickness absence lasting 1 month or more. Methods: Participants were 7,343 male and 7,344 female financial service company employees who completed the BJSQ. We obtained personnel records covering a 1-year period to identify employees with long-term sickness absence, which was treated as a dichotomous variable. Participants were classified into four groups (high-stress+dissatisfied, high-stress+satisfied, not high-stress+dissatisfied, and not high-stress+satisfied groups) to calculate the hazard ratios (HRs) of long-term sickness absence for these groups using Cox’s proportional hazard regression analysis. Furthermore, to examine whether the combined effect of high stress and job dissatisfaction is synergistic or additive, we calculated relative excess risk due to interaction (RERI), attributable proportion due to interaction (AP), synergy index (SI), and their 95% confidence intervals (CIs). Results: After adjustment for covariates, the HR of long-term sickness absence was highest among the high-stress+dissatisfied group (HR 6.49; 95% CI, 3.42–12.3) followed by the high-stress+satisfied group (HR 5.01; 95% CI, 1.91–13.1). The combined effect of high stress and job dissatisfaction was additive (95% CIs of RERI and AP included 0 and that of SI included 1). Conclusions: Our findings suggest incorporating high stress with job dissatisfaction improves the predictability of long-term sickness absence. However, employees reporting high stress but satisfaction with their jobs may still at increased risk of developing long-term sickness absence.
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