Table 2.

Established cohort studies of childhood T1D in the included metabolomic and lipidomic publications.

No.	Cohort study	Center location	Launch time	Recruitment	Study type	Subject enrollment	Number	Groups	Age	Genetic risk/family history	Samples	Visit design
1	BABYDIAB	Germany	1989	12 years	Longitudinal cohort study	With parents diagnosed as T1D or with mothers diagnosed with gestational diabetes	1,650 Children	Children progressing to T1D during follow-up; children developing autoantibodies at different onset times; controls	From birth to 20 years of age	Having parents with T1D or mothers with gestational diabetes	Cord blood, blood	Venous blood samples were obtained from children at study visits scheduled at 9 months and 2, 5, 8, 11, 14, 17, and 20 years of age
2	Diabetes Autoimmunity Study in the Young (DAISY)	Denver, Colorado, USA	1993	7 years	Longitudinal cohort study	First-degree relatives of patients with T1D and general population children with HLA DR-DQ genotypes	2,547 Children	Children developed T1D; children developed persistent IA and were islet autoantibody-positive at their last study visit; control	From birth to a mean of 4 years (9 months to 9 years of age)	First-degree relatives of patients with T1D (FDRs) and general population children with T1D-susceptibility HLA DR-DQ genotypes	Cord blood, blood	Blood samples were obtained every 3–6 months from birth. Diet data were collected at 3, 6, 9, 12, and 15 months of age
3	Type 1 Diabetes Prediction and Prevention Study (DIPP)	Turku, Oulu in Finland	1994	6 years	Longitudinal cohort study	Born in three centers; at increased genetic risk	Enrollment: 31,526; follow-up: 4,651	Children progressing to T1D during follow-up; children developing only one autoantibody; children developing two autoantibodies; children developing three or four autoantibodies; controls	From birth to 15 years of age	With HLA-DQB1 genotypes  ∗02/ ∗0302 and  ∗0302/x (x is not  ∗02,∗0301,  ∗0602)	Cord blood, blood, stool	In Turku: monitored at 3-month intervals until 2 years of age and then twice a year; In Oulu and tampere: at the ages of 3, 6, 12, 18, and 24 months and then once a year
4	Environmental Causes of Type 1 Diabetes (MIDIA)	Norway	2001	7 years	Longitudinal cohort study	With a high genetic risk for T1D	Genotyping: around 47, 000; follow-up: more than 900	Children progressing to T1D during follow-up; children developing autoantibodies with different numbers; controls	From birth to 15 years of age	With a high genetic risk for T1D	Blood	Blood samples and questionnaires were obtained at the age of 3, 6, 9, and 12 months, and then annually
5	The Environmental Determinants of Diabetes in the Young Study (TEDDY)	USA, Finland, Sweden, Germany	2007	5 years	Longitudinal cohort study	Younger than 4 months; with specific HLA genotypes, or FDRs of T1D patients	Screening: 3,61,588; enrollment: 17,804; follow-up: over 7,800	Children progressing to T1D during follow-up; children having a different initial autoantibody (IAA-first, GADA-first, IA–2A) with different onset time; children developing more than one autoantibody during follow-up (mAb+); controls	From birth to 15 years of age	With HLADR-DQ haplogenotypes for the risk of T1D; from families with first-degree relatives diagnosed as T1D	Blood, stool, tap water, toenail clippings	From 2 to 14 weeks and 25–28 weeks of the pregnancy and delivery; every 3 months for the first 4 years and until 15 years
6	Diabetes Prediction in Skåne (DiPiS)	Skåne region of Southern Sweden	2000	5 years	Case–control matched cohort study	At increased risk for type 1 diabetes and islet autoantibody appearance	Screening: 33,682 mothers, more than 35,000 newborns	Children progressing to T1D at different times during follow-up; controls	From birth to 10 years of age	At increased risk for type 1 diabetes and islet autoantibody appearance	Cord blood	Every 4–12 months, depending on the number of islet autoantibodies
7	The Danish Remission Phase Study	Denmark	2004	3 years	Prospective observational study	Children and adolescents aged less than 17 years newly diagnosed with T1D	129 children and adolescents	Children and adolescents diagnosed with T1D	12 months after diagnosis	Not mentioned	Blood	Blood samples were collected prospectively 1, 3, 6, and 12 months after diagnosis