Barts and The London School of Medicine and Dentistry, and Asthma UK Centre for Applied Research, Queen Mary University of London, London, UK. Electronic address: d.a.jolliffe@qmul.ac.uk. Department of Emergency Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA. School of Population Health, University of Auckland, Auckland, New Zealand. Department of Pediatrics, St Michael's Hospital, Toronto, ON, Canada. Bone Mineral Research Center, Winthrop University Hospital, Mineola, NY, USA. Department of Nutrition, Harvard TH Chan Shool of Public Health, Boston, MA, USA. Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden. Department of Geriatric Medicine and Aging Research, University Hospital Zurich, Zurich, Switzerland. Department of Pediatric Infectious Diseases and Immunology, School of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile. Department of Nutrition, Exercise and Sports, University of Copenhagen, Frederiksberg, Denmark. Exercise, Lifestyle and Nutrition Clinic, Edmond and Lily Safra Children's Hospital, Tel Hashomer, Israel. Paediatric Clinic, Department of Medicine and Surgery, University of Parma, Parma, Italy. Department of Non-Communicable Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK. Department of Emergency Medicine, University of Colorado School of Medicine, Aurora, CO, USA. Saban Pediatric Medical Center, Soroka University Medical Center, Faculty of Health Sciences, Ben-Gurion University, Beer Sheva, Israel. Department of Health Research Methods, Evidence and Impact, McMaster University, Hamilton, ON, Canada. Department of Paediatrics: Child and Youth Health, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand. Barts and The London School of Medicine and Dentistry, and Asthma UK Centre for Applied Research, Queen Mary University of London, London, UK. Department of Pediatrics, Case Western Reserve University School of Medicine, Cleveland, OH, USA; University Hospitals Rainbow Babies and Children's Hospital, Cleveland, OH, USA. Universitair Ziekenhuis Leuven, Leuven, Belgium. Hirabai Cowasji Jehangir Medical Research Institute, Maharashtra, India. Faculty of Medicine and Health Technology, University of Tampere, Tampere, Finland; Centre for Military Medicine, Helsinki, Finland. Division of Pediatric Hematology, Oncology, and Stem Cell Transplantation, Columbia University Medical Center, New York, NY USA. Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada. Department of Pediatric Pulmonology, Medical University of Lodz, Lodz, Poland. Department of Statistics, The Pennsylvania State University, Hershey, PA, USA. Department of Public Health, Epidemiology and Biostatistics, Institute of Applied Health Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK. Department of Pathology, University of Otago, Christchurch, New Zealand. Jikei University School of Medicine, Tokyo, Japan. Population Health Department, QIMR Berghofer Medical Research Institute, QLD, Australia. Department of Epidemiology, Geisel School of Medicine at Dartmouth, Lebanon, NH, USA. Children's Hospital, Pediatric Research Centre, University of Helsinki and Helsinki University Hospital, Helsinki, Finland. Department of Paediatrics, University College of Medical Sciences, Delhi, India. FANCL Research Institute, FANCL Corporation, Yokohama, Japan. Neuroepidemiology Unit, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, VIC, Australia; Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, Australia. Institute of Home Economics, University of Delhi, New Delhi, India. Barts and The London School of Medicine and Dentistry, and Asthma UK Centre for Applied Research, Queen Mary University of London, London, UK. Electronic address: a.martineau@qmul.ac.uk.