How should interventions to reduce inequalities in health be evaluated?

OBJECTIVE The effectiveness of interventions which have been proposed or are currently in progress to reduce socioeconomic inequalities in health is largely unknown. This paper aims to develop guidelines for evaluating these interventions. APPROACH Starting from a set of general guidelines which was recently proposed by a group of experts reporting to the national Programme Committee on Socioeconomic Inequalities in Health in The Netherlands, an analysis was made of the appropriateness of different study designs which could be used to assess the effectiveness of interventions to reduce inequalities in health. RESULTS A "full" study design requires the measurement, in one or more experimental populations and one or more control populations, of changes over time in the magnitude of socioeconomic inequalities in health. This will usually imply a community intervention trial. Five alternative study designs are distinguished which require less complex measurements but also require more assumptions to be made. Several examples are given. CONCLUSIONS Building up a systematic knowledge base on the effectiveness of interventions to reduce socioeconomic inequalities in health will be a major enterprise. Elements of a strategy to increase learning speed are discussed. Although the guidelines and design recommendations developed in this paper apply to the evaluation of specific interventions where rigorous evaluation methods can often be used, they may also be useful for the interpretation of the results of less rigorous evaluation studies, for example of broader policies to reduce socioeconomic inequalities in health.