In addition to questions that can be answered by the randomised trial, we have also created a bioresource of the 50,000 trial participants to address other epidemiological questions, particularly those relating to genetics.

In all participants, we have:

• collated basic lifestyle and self-reported health nformation using a web-based questionnaire;
• assayed a genome-wide genotyping array containing >800,000 genetic variants;imputed from this array backbone to >80 million variants;
• used a Sysmex haematology analyser to assay >50 blood cell parameters;assessed ~230 metabolites using a NMR platform covering lipoproteins, lipids and low molecular weight metabolites.

In subsets of participants, we have:

• conducted high-depth (50x) whole exome sequencing;conducted low-pass (15x) whole genome sequencing;measured thousands of soluble proteins using a novel aptamer-based assay approach;
• assayed >1000 metabolites using a mass-spectrometry platform;
• assayed >400 lipid species using a bespoke mass-spectrometry platform;
• measured candidate biomarkers of relevance to blood donation (eg, iron-related markers);
• assessed cognitive function using a validated four-domain online testing platform.