Often the discussion is framed in the context of genomic research and the exploration of gene-environment interactions, but many branches of science, including behavioural epidemiology, will benefit from having data on very large numbers of participants. Much has been written of the need for very large-scale studies in contemporary epidemiology and public health. These documents, made available through the ICAD website, may also serve as a guide to others undertaking similar projects. Key to this process is the rigorous conduct and reporting of retrospective data harmonisation, which is essential to the appropriate analysis and interpretation of derived data. The project to expand ICAD further demonstrates the feasibility of pooling data on physical activity, sedentary behaviour and potential determinants from multiple studies. An expanded ICAD database was made available in May 2017. Guidance documents and facilities to enable the creation of new harmonised variables were also devised and made available to ICAD users. A set of core harmonised variables, including parent education, ethnicity, school travel mode/duration and car ownership, were derived for use by the research community. Work to expand ICAD has increased the number of studies with longitudinal accelerometer data, and expanded the breadth of behavioural, social and environmental characteristics that can be used as exposure variables. Extensive documentation, describing the source data and harmonisation procedure, was prepared and made available through the ICAD website. Harmonised variables were derived iteratively, with input from the ICAD investigators and a panel of invited experts. All data were collated into a single repository for cataloguing and harmonisation. Methodįollowing a consultation process, ICAD partners were requested to share accelerometer data and information on selected behavioural, social, environmental and health-related constructs. In this paper, we describe the acquisition, management and harmonisation of non-accelerometer data in a project to expand the International Children’s Accelerometry Database (ICAD). Where this approach is used, transparency of the methodology for data collation and harmonisation is essential to enable appropriate analysis and interpretation of the derived data. One route to achieving this is through the pooling and co-analysis of data from multiple studies.

Large, heterogeneous datasets are required to enhance understanding of the multi-level influences on children’s physical activity and sedentary behaviour.

Icad 2017