Combining information to answer epidemiological questions about a target population.

Epidemiologists are attempting to address research questions of increasing complexity by developing novel methods for combining information from diverse sources. Cole et al. (Am J Epidemiol. 2022;XXX(XX):XXXX-XXXX) provide two examples of combining information to draw inferences about a population proportion. In this commentary, we consider combining information to learn about a target population as an epidemiological activity and distinguish it from more conventional meta-analyses. We examine possible rationales for combining information and discuss broad methodological considerations, with an emphasis on aspects of study design, including the selection among candidate data sources and the sampling of observations from these sources.