Jonas F Ludvigsson1,2,3,4. 1. Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden. 2. Department of Pediatrics, Örebro University Hospital, Örebro, Sweden. 3. Division of Epidemiology and Public Health, School of Medicine, University of Nottingham, Nottingham, UK. 4. Celiac Disease Center, Department of Medicine, Columbia University College of Physicians and Surgeons, New York, NY, USA.