The EU Child Cohort Network's core data: establishing a set of findable, accessible, interoperable and re-usable (FAIR) variables

Abstract

The Horizon2020 LifeCycle Project is a cross-cohort collaboration which brings together data from multiple birth cohorts from across Europe and Australia to facilitate studies on the influence of early-life exposures on later health outcomes. A major product of this collaboration has been the establishment of a FAIR (findable, accessible, interoperable and reusable) data resource known as the EU Child Cohort Network. Here we focus on the EU Child Cohort Network's core variables. These are a set of basic variables, derivable by the majority of participating cohorts and frequently used as covariates or exposures in lifecourse research. First, we describe the process by which the list of core variables was established. Second, we explain the protocol according to which these variables were harmonised in order to make them interoperable. Third, we describe the catalogue developed to ensure that the network's data are findable and reusable. Finally, we describe the core data, including the proportion of variables harmonised by each cohort and the number of children for whom harmonised core data are available. EU Child Cohort Network data will be analysed using a federated analysis platform, removing the need to physically transfer data and thus making the data more accessible to researchers. The network will add value to participating cohorts by increasing statistical power and exposure heterogeneity, as well as facilitating cross-cohort comparisons, cross-validation and replication. Our aim is to motivate other cohorts to join the network and encourage the use of the EU Child Cohort Network by the wider research community.

Keywords: Birth cohort; Cross-cohort collaboration; Data harmonisation; FAIR (findable, accessible, interoperable and reusable) principles; Lifecourse epidemiology.

Fig. 1

The process adopted in LifeCycle to establish and harmonise the core variables for the EU Child Cohort Network

Fig. 2

An illustration of the EU Child Cohort Network Variable Catalogue displaying the LifeCycle variable “maternal history of asthma before pregnancy”. Displayed is a description of the target EU Child Cohort Network variable and how the variable was harmonised in two separate cohorts. Note: descriptions from two separate cohorts are displayed on the same page for illustrative purposes only

Fig. 3

An illustration of the EU Child Cohort Network Variable Catalogue’s menu structure giving an overview of the themes included in the EU Child Cohort Network and the number of variables included in each theme. ¹Including yearly-repeated variables with up to 18 measures between the ages of 0 and < 18 years. ²Including weekly-repeated variables with up to 43 measures taken between gestational weeks 0 and < 43. ³Including trimester-repeated variables with separate measures for the first, second and third trimesters. ⁴Including separate variables indicating the type of father the variable relates to (biological, social father, social mother, unknown). ⁵Including separate variables relating to secondary father-figures. ⁶Including monthly-repeated variables with up to 216 measures between the ages of 0 and < 216 months. ⁷Including yearly-repeated variables with up to four measures between the ages of 0 and < 4 years. ⁸Including yearly-repeated variables with up to 13 measures between the ages of 0 and < 13 years

Fig. 4

Percentage of EU Child Cohort Network core variables harmonised by each cohort. The figure displays the percentage of the 123 core variables listed in Online Resource 1 (excluding meta-variables) harmonised by each cohort. Shading of bars displays the degree of matching within each cohort: black bars represent percentage of completely harmonised variables; dark grey bars represent percentage of partially harmonised variables; light grey bars represent percentage of variables that were not harmonizable (impossible harmonisation)

Fig. 5

Harmonised non-repeated core variables in the EU Child Cohort Network. Bars display the number of children with either a partially (grey bars) or completely (black bars) harmonised core variable for each of the main themes/exposures. The dashed line represents the total number of children (240,684), as of June 2020, contributing data to the EU Child Cohort Network with all three of the following variables harmonised: (1) birth weight, (2) sex, (3) at least one height or weight measurement taken at ≥ 1 year. COB country of birth, PE pre-eclampsia, gest. HT gestational hypertension, size for GA size for gestational age

Fig. 6

Number of children in the EU Child Cohort Network with yearly-repeated measure core variables. Bars display the number of children with at least one measure between the ages of zero and three (child-care variables) or zero and seventeen (all other variables), either partially (grey bars) or completely (black bars) harmonised. The dashed line represents the total number of children (240,684), as of June 2020, contributing data to the EU Child Cohort Network with all three of the following variables harmonised: i) birth weight, ii) sex, iii) at least one height or weight measurement taken at ≥ 1 year

Fig. 7

Weight and height data in the EU Child Cohort Network. Graphs display a number of children in the network with at least one weight (dark grey bars) or height (light grey bars) measure at < 3 months, 3–6 months, 6–12 months and yearly intervals from 1 to 17 years; b total number of weight (dark grey bars) and height (light grey bars) within each age band (i.e. one child may contribute multiple measurements within each age band)