Understanding the Health Inequality Paradox: A Meta-Analysis of the Effect of Study Design on Health Inequality Outcomes and Welfare Regime Patterns in Comparative Health Inequality Research.

Comparative research on social health inequalities focuses on the structural determinants, but results so far are inconclusive. Studies on the impact of welfare state arrangements on social health inequality either find that universal welfare states are beneficial for social health equity or the opposite – a health inequality paradox. Until now, this puzzle has not been evaluated systematically and comprehensively. To help resolve this, building upon various theoretical discussions and previous systematic reviews, I hypothesize that study design characteristics affects the measured extent of health inequalities and, thus, contribute to the appearance of a paradox.

In this meta-analysis, I used data from 39 publications identified through systematic searches of four literature databases (PubMed, ASSIA, Web of Science, Sociological Abstracts) and reference lists of four systematic reviews. Included publications consider individuals of any age in OECD countries with a cross-sectional and comparative study design examining educational, occupational, income and wealth inequalities in physical health. First, using a hierarchical mixed effects regression model, I estimate how much variance in effect sizes is explained by study design characteristics. Second, I calculate average effect sizes for each country accounting for study design characteristics.

Results to be presented at the conference will show that certain study design characteristics have effects on the extent of measured health inequalities. Therefore, my findings will highlight the impact of study design choice on the measurement and interpretation of results, especially in comparative studies. By taking study design characteristics into account, I can show the extent of health inequalities for each country, free of the obscuring effects of study design. In this way, I will contribute to solving the public health puzzle on the health inequality paradox.