Box 1.

A glossary of the key elements and concepts in LifeCycle

Term	Definition
Complete harmonisation	The ability to derive the variable as described in the harmonization manual, both in definition and format
Data harmonisation	The process of creating a common dataset from disparate datasets
DataSHIELD	An infrastructure and series of R packages that enables the remote and non-disclosive analysis of individual participant data
EU Child Cohort Network	A network bringing together existing data from more than 250,000 European and Australian children and their parents
Federated data analysis	Centralised analysis of individual participant data where data are stored on local servers and do not leave the host institution
Harmonisation manual	A manual containing a list of target variables together with instructions for their harmonisation
Impossible harmonisation	The complete inability to derive the variable due to no or limited information
Horizon2020 LifeCycle Project	A collaboration between scientists from more than 17 existing pregnancy and child cohort studies
EU Child Cohort Network Variable Catalogue	An online catalogue providing an overview of available data in the EU Child Cohort Network, including details of how data have been created (http://catalogue.lifecycle-project.eu)
LifeCycle core variables	A set of basic variables, derivable by the majority of cohorts participating in LifeCycle and frequently required in lifecourse analyses
Opal	A data warehouse that is integrated with R and the DataSHIELD platform, allowing the analysis of data without the physical sharing or disclosing of individual participant data
Partial harmonisation	The ability to derive the variable as described but with some loss of information