The study is part of the ALSPAC large grant (ESRC), project code B273.

In this study, we aim to examine the effects of childhood obesity and child height on children's educational outcomes. As the relationships between child weight or height and educational attainment are likely to be subject to confounding in observational studies, we wish to test the feasibility of using associated genotypes as instruments in Mendelian randomisation experiments. Within the ALSPAC cohort, data have already been collected on a series of single nucleotide polymorphisms, which are robustly associated with both height and body mass index (BMI), as has been confirmed by large independent studies. As such, we wish to use these (and other available data relating to these intermediate traits of interest) in instrumental variable analyses, allowing us to reappraise the observational relationships between these anthropometric measures and education.

We are conscious of the potential limitations of power within this setting, given that the genetic effects on the intermediate trait are relatively small and the variation in these traits required to shift educational attainment relatively large. However, it will be possible to assess the plausibility of studies such as this with data already collected in the ALSPAC cohort. At this stage, we only seek access to already available data.

As we already have access to the ALSPAC data on child and family background characteristics, we only wish to obtain the genetic markers related to children's obesity and height. We understand we cannot use the individual case identifiers we already have. So if needed, we are happy to provide you with the raw data we are using, so that you can merge in the genotypes and provide us with a new child ID for this study.