HEAF is a cohort study that follows individuals over the age of 50 years. Participants are patients registered with participating practices, and general practitioners (GPs) reviewed the sampling lists before mailing and excluded patients whom they thought should not be approached (e.g. because of terminal illness or recent bereavement). Over 8,000 male and female participants were recruited from 24 general practices across England, and were followed annually for the first five years of the study.