Appendix 1.

Cohort studies shown in publications in 2008–2017

Study	Year	Country	Period	Birth	Register of asthma	Age of asthma diagnosis
Tollanes et al. [10]	2008	Norway	1967–1998	Single	The Norwegian National Insurance Scheme (NIS)	< 18 years old
Davidson et al. [4]	2010	UK – England	1970–1989	Single	Registry of Hospital admission or hospital-based day care for asthma (ORLS)	< 18 years old
Magnus et al. [11]	2011	Norway	2001–2007	Single	Questionnaire	< 3 years old
Van Nimwegen et al. [12]	2011	Netherlands	2000–2003	Single	Questionnaires in the International Study on Asthma and Allergy in Childhood (ISAAC)	6–7 years old
Almqvist et al. [13]	2012	Sweden	1993–1999	Siblings	The National Patient Register (NPR)	13 years old Asthma diagnosis during follow-up year
Braback et al. [14]	2013	Sweden	1999–2006	Single	The Swedish National Board of Health and Welfare and Statistics, Sweden	Cohort 1: 2–5 years old Cohort 2: 6–9 years old
Black et al. [5]	2015	UK – Scotland	1993–2007	Single	The Scottish Morbidity Record SMR02 and SMR01	6 years old
Bruske et al. [7]	2015	Germany	1995–1998	Single	Spirometry tests, doctor diagnoses	15 years old
Van Berkel et al. [15]	2015	Netherlands	2002–2006	Single	Questionnaires in the International Study on Asthma and Allergy in Childhood (ISAAC)	6 years old
Black et al. [6]	2016	UK – Scotland	1993–2007	Single	The Scottish Morbidity Record SMR02 and SMR01	6 years old
Sevelsted et al. [8]	2016	Denmark	1998–2010	Single	The National Prescription Registry and the Danish National Patient Registry	< 7 years old
Brix et al. [3]	2017	Denmark	1997–2012	Twins	The Danish National Patient Registry	15 years old