Psychometric properties and differential explanation of a short measure of effort-reward imbalance at work: A study of industrial workers in Germany

Background: We test the psychometric properties of a short version of the Effort-Reward Imbalance (ERI) questionnaire in addition to testing an interaction term of this model's main components on health functioning. Methods: A self-administered survey was conducted in a sample of 2,738 industrial workers (77% men with mean age 41.6 years) from a large manufacturing company in Southern Germany. The internal consistency reliability, structural validity, and criterion validity were analyzed. Results: Satisfactory internal consistencies of the three scales: "Effort", "reward", and "overcommitment", were obtained (Cronbach's alpha coefficients 0.77, 0.82, and 0.83, respectively). Confirmatory factor analysis showed a good model fit of the data with the theoretical structure (AGFI=0.94, RMSEA=0.060). Evidence of criterion validity was demonstrated. Importantly, a significant synergistic interaction effect of ERI and overcommitment on poor mental health functioning was observed (odds ratio 6.74 (95% CI 5.32-8.52); synergy index 1.78 (95% CI 1.25-2.55)). Conclusions: This short version of the ERI questionnaire is a reliable and valid tool for epidemiological research on occupational health.