What is the ″golden standard″ for assessing population-based interventions? - Problems of dilution bias

Abstract

Objectives - To identify different types of dilution bias in population-based interventions and to suggest measures for handling these methodological problems. Design - Literature review plus analysis of data from a population-based intervention against cardiovascular disease in a Swedish municipality. Main results - The effects of an intervention on mortality and morbidity were much more diluted by non-intervening factors, dissemination to areas outside the intervention area, social diffusion, population mobility and time than by using intermediate outcome measures. Conclusions - Theoretically, changes in scientifically well documented risk factors, for example, intermediate outcome measures, should be preferred to using morbidity or mortality as outcome measures.