Misclassification of occupation-based socioeconomic position and gender comparisons of socioeconomic risk

Aims: Because occupational classification systems tend to be less precise in the female sector of the working market there has been concern that this might imply more misclassification of socioeconomic position among women, biasing comparisons of gender-specific socioeconomic differences in risk. Methods: The Stockholm Heart Epidemiology Program (SHEEP) is a population-based case-control study of risk factors for incident myocardial infarction. The study base included all Swedish citizens aged 45-70 in Stockholm County during 1992-94, 550 female and 1201 male cases, and 776 female and 1538 male controls. The use of an occupational classification as the base for categorizing socioeconomic position was compared with socioeconomic position based on detailed self-reported information on job titles and work tasks. Results: Women are categorized into fewer occupational categories than men and the socioeconomic heterogeneity within occupational categories is substantial for women as has been reported by others. However, despite more occupational categories for male types of jobs the socioeconomic heterogeneity within occupational categories is actually larger for men, implying larger misclassification among men. In simulations with different levels of socioeconomic misclassification among women, the effects on the gender comparison of socioeconomic differences in disease risk were small and they were mostly compensated for by less misclassification among men. Conclusions: The findings do not support the assumption that misclassification of socioeconomic position among women due to a restricted working market and a crude occupational classification for female jobs is an important issue when comparing measures of socioeconomic inequalities in health between men and women.