Jan studied medicine at the University of Groningen (1985) and received a PhD (neurology / medical physics) from the University of Utrecht (1989). Since 1990, he has worked as a clinical epidemiologist in the Netherlands and the UK. Jan joined the London School of Hygiene and Tropical Medicine in January 2000. He collaborates with the Royal College of Surgeons of England (from 2001 to 2011 as the Director of the College’s Clinical Effectiveness Unit) and also advises the Royal College of Obstetricians and Gynaecologists on research and audit since 2006.