Participant recruitment, retention, and engagement with enhancement projects has benefited from the willingness of very large numbers of British people to take part in observational research without the prospect of direct personal gain [15]. Participants spent an average of about two and a half hours at the recruitment visit. All gave broad consent to use of their anonymised data and samples for any health-related research, to be re-contacted for further substudies, and for UK Biobank to access their health-related records. Large subsets have subsequently completed Web-based questionnaires, agreed to wear a physical activity monitor, and repeated the entire baseline assessment. Of those who attended the first repeat assessment visit and provided feedback, 92% reported that they would be willing to travel for up to two hours for an imaging assessment visit lasting half a day. UK Biobank keeps its participants involved through providing progress updates via its website, with annual newsletters, and through its dedicated Participant Resource Centre (PRC), enabling them to continue to support the project and participate in research over the years ahead.
