Multiple measures of socio-economic position and psychosocial health: proximal and distal measures

Background The aim of this paper is to compare three models for exploring the links between different measures of adult socioeconomic position (SEP)-education, occupation, income-and psychosocial health. Model I is a basic univariate regression model with psychosocial health as the outcome and a measure of SEP as the predictor. Model II is a multiple regression model with psychosocial health as the outcome with all three measures of SEP allocated the same temporal position as predictors. Model III treats education, a distal measure of SEP, as antecedent to the proximal measures of SEP in the prediction equations linking SEP to health. Methods Participants were drawn from the Whitehall II study, a prospective cohort study of British civil servants. Data analysed here are from Phase 5 (1997-1999) of data collection, 7830 individuals in all. The measures of SEP and psychosocial health were assessed via a self-administered questionnaire. Results The three models can lead to completely different conclusions. Model III, our preferred model, shows education to have a stronger indirect effect on psychosocial health when compared to its direct effect. The indirect effect is due to the effect of education on proximal measures of social position, occupation, and income in this case. Conclusions Results reported here support the hypothesis that a comparison of the relative importance of the different measures of social position in predicting health is meaningless if the causal relationships among these measures are not accounted for.