Measuring social inequalities in health -: politics or science?

Aims: The methods chosen for seeking the answers to questions on social inequalities in health may heavily influence the results and thereby the formulation of appropriate public health policies. This study aims at identifying methodological problems in analysing trends about socio-economic differences in health. The focus is on whether the results may be influenced by the choice of outcome measure, the choice of social groups or by changes in the composition of social groups over time. Methods: Data sets on socio-economic differences in mortality in Europe presented by Kunst et al. and also data sets from the Swedish Survey of Living Conditions have been used. Results: The choice of outcome measures influences the results. Mortality trend comparisons between European countries for different socio-economic groups give completely different pictures whether using relative or absolute figures. The generally lower death rate in Sweden means that even small absolute differences give higher relative differences than in countries with higher death rates. Using socio-economic group or educational level as indicators of social position showed quite different results when analysing social inequalities in smoking and overweight in Sweden. The structure of social groups changes over time making trend analysis more difficult to interpret. In Sweden the group of poorly-educated people has halved in size during the past two decades, and the group of highly-educated people has increased. These changes most likely make the poorly-educated group a more homogenous and -healthwise - a more negatively selected group than it was twenty years ago. Conclusions: The most appropriate scientific approach to this problem is to present basic data in terms of absolute figures per population before presenting relative or absolute differences.