To examine whether the psychometric properties of the effort-reward imbalance (ERI) at work scales could be replicated with post-myocardial infarction (post-MI) patients and to measure the criterion validity through its association with psychological distress.
A cross-sectional survey was conducted among 814 patients (739 men and 75 women) who had returned to work after their first MI and who were followed up by telephone at an average of 2.2 years after their baseline interview (1998-2000). The psychological demands scale of the Karasek Job Content Questionnaire was used to measure effort. Reward was measured with nine items from the original reward scale by Siegrist plus two proxy items. Exploratory and confirmatory factor analyses were used to test the theoretical structure of ERI. Using log-binomial regression models, we evaluated the association between ERI scales and psychological distress measured with the 14-item Psychiatric Symptom Index.
ERI scales and subscales demonstrated adequate internal consistencies. Exploratory factor analysis using oblique (promax) rotation yielded a three-factor solution with items representative of extrinsic effort (Factor 1) and reward subscales (Factors 2 and 3). Confirmatory factor analysis demonstrated a good fit with the data. The internal consistencies and discriminant validities of the ERI scales were satisfactory. Furthermore, effort, reward, and ERI ratio were significantly associated with psychological distress (adjusted prevalence ratio [PR] = 1.71, 95% confidence interval [CI] = 1.26-2.31; PR = 1.63, 95% CI = 1.16-2.29; and PR = 1.70, 95% CI = 1.17-2.47, respectively).
The psychometric properties of the ERI scales were generally reproduced among post-MI patients. The associations with psychological distress supported the criterion validity of the ERI scales in this population.
CFA = confirmatory factor analysis;
CHD = coronary heart disease;
CI = confidence interval;
EFA = exploratory factor analysis;
ERI = effort-reward imbalance;
LVEF = left ventricular ejection fraction;
MET-h/week = metabolic equivalent task-hours per week;
MI = myocardial infarction;
PR = prevalence ratio