Cohort profile: Health and Attainment of Pupils in a Primary Education National Cohort (HAPPEN) - a hybrid total population cohort in Wales, UK.

Purpose: Health and Attainment of Pupils in a Primary Education National (HAPPEN) is a primary school national cohort which brings together education, health and well-being research in line with the Curriculum for Wales framework. Health, education and social care data are linked and held in the Secure Anonymised Information Linkage (SAIL) Databank. In addition, school-aged children complete the HAPPEN Survey to inform the design and implementation of the Health and Well-being curriculum.