Meta-analysis of observational studies

Observational studies such as those used to investigate lifecourse epidemiology present particular challenges for meta-analysis. This chapter discusses the differences between meta-analysis of randomised controlled trials and observational studies, introduces methods for meta-analysis in this unique setting, and illustrates the issues involved using a real example from a meta-analysis in the field of diet and cancer. Emphasis is placed on practicalities of how to conduct meta-analyses of observational studies where the information presented in the articles reviewed may be limited.