While there are hypotheses and preliminary data as to the etiology of type 1 diabetes (T1D), the data are often limited by imprecise assessment of exposure, recall bias, failure to account for genetic susceptibility, failure to assess exposures at very early ages, or the inability to follow a sufficient sample of children long-term with high intensity. The Environmental Determinants of Diabetes in the Young (TEDDY) study is a multicenter prospective cohort study that was established in response to these gaps in understanding of T1D. The primary objectives of the study include identifying environmental factors—such as infectious agents, dietary factors, and psychosocial factors—that trigger or protect against the development of islet autoimmunity and T1D and examining genetic-environmental interactions to investigate interactive effects that contribute to T1D.

The TEDDY study was designed to follow children with and without a family history of T1D to understand the environmental factors that contribute to the disease. Newborn children younger than 4 months were screened for high-risk HLA alleles, and those with qualifying haplotypes were eligible for follow-up. Information is collected on medical information (infections, medication, immunizations), exposure to dietary and other environmental factors, negative life events, family history, tap water, and measurements of psychological stress. Biospecimens, including blood, stool, urine, and nail clippings, are taken at baseline and follow-up study visits. The primary outcome measures include two endpoints—the first appearance of one or more islet cell autoantibodies (GADA, IAA, or IA-2A), confirmed at two consecutive visits, and development of T1D. The cohort will be followed for 15 years, or until the occurrence of one of the primary endpoints.

The TEDDY data currently available include screening phase data, baseline phase data, study phase clinical data, and multiple analysis datasets. Data collection began in 2004 and is still on-going.

The primary objectives of the study include identifying environmental factors, specifically infectious agents, dietary factors, and psychosocial factors, that trigger or protect against the development of islet antibodies or T1D and examining genetic-environmental interactions to investigate the mechanisms of these interactive effects.

There are two primary outcome measures for this study: (1) the first appearance of one or more islet cell autoantibodies (GADA, IAA, IA-2A), confirmed at two consecutive visits, and (2) development of T1D. Additionally, there are two secondary outcome measures for this study: (1) celiac disease and (2) celiac disease autoimmunity (CDA)

Newborns less than 4 months of age with either a high-risk HLA haplotype or a first-degree relative affected with T1D were eligible for enrollment.

Patients with an illness or birth defect that precludes long-term follow-up or involves use of treatment that may alter the natural history of diabetes (e.g., steroids or insulin) were excluded from the study.

This study is ongoing.