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Article History

Received: 2 September 2025

Revised: 12 February 2026

Accepted: 17 March 2026

First Online: 6 April 2026

Competing interests

: The authors declare no competing interests.

: Ethical approval was obtained from the national ethics committees for each study centre: Ethics Committee of the Gent University Hospital (15/10/2007, ref: No. EC UZG 2007/243 and 19/02/2013, No. B670201316342), Belgium; Cyprus National Bioethics Committee (12/07/2007, ref: No. EEBK/EM/2007/16 and 21/Feb/2013, No. EEBK/ETI/2012/33), Nicosia, Cyprus; Tallinn Medical Research Ethics Committee (14/06/2007, ref: No. 1093 and 17/January 2013, No. 128), Tallinn, Estonia; Ethics Committee of the University of Bremen (16/01/2007 and 11/12/2012), Bremen, Germany; Medical Research Council (21/06/2007, ref: 22–156/2007-1018EKU and 18/12/2012, 4536/2013/EKU), Hungary; Ethics Committee of the Local Health Authority (19/06/2007, ref: No. 2/CE and 18/Sep/2012, No. 12/12), Avellino, Italy; Bioethical Committee of the University of Rzeszów (05/06/2013 and 01/12/2015), Rzeszów, Poland; Ethics Committee for Clinical Research of Aragon (20/06/2007, ref: No. PI07/13 and 13/Feb/2013, No. PI13/0012), Zaragoza, Spain; Regional Ethics Research Board (30/07/2007, ref: No. 264-07 and 10/Jan/2013, No. 927−12), Gothenburg, Sweden. The IDEFICS and I.Family study protocols adhered to the Declaration of Helsinki ethics principles for research that includes human subjects. Participant inclusion required that parents give written informed consent for their children, and young children also gave verbal consent. From the age of 12 years onwards, children gave their own written informed consent in plain language. The Pan-European IDEFICS/I.Family children cohort study is registered in the ISRCTN clinical trial registry: ).