TEDDY Overview
What causes type 1 diabetes (T1D)—and can we stop it before it starts? That’s the question at the heart of TEDDY: The Environmental Determinants of Diabetes in the Young. This groundbreaking international study followed more than 8,600 children with high genetic risk for T1D from infancy through age 15 over six sites across the globe, making it the largest and most detailed study of its kind.
TEDDY was designed to uncover which environmental factors—such as infections, diet, stress, or chemical exposures—might trigger the onset of T1D in children who are genetically predisposed. Researchers also examined links between T1D and other autoimmune conditions, like celiac disease. Over nearly two decades, TEDDY has built the world’s largest resource for understanding how type 1 diabetes begins—and how we might prevent it.
The study is a global collaboration supported by the National Institutes of Health (including NIDDK, NIAID, NICHD, and NIEHS), the Centers for Disease Control and Prevention (CDC), and the Juvenile Diabetes Research Foundation (JDRF).
PNRI is proud to be one of six research centers that conducted TEDDY, and the only site on the U.S. West Coast. Other centers were located in Colorado, Georgia, Florida, Finland, Germany, and Sweden. A total of 8,667 families participated across all sites—including 1,378 through PNRI—contributing decades of data and biological samples to this effort. Their involvement was extraordinary—not only in scale, but in spirit. Many families shared personal reflections on their experience with TEDDY and what being part of this groundbreaking study meant to them. You can read their messages here.
Sample collection concluded in February 2025, but the work continues. TEDDY’s extensive biobank—containing more than 850,000 biological samples—offers an unmatched window into the earliest origins of autoimmune disease, laying the groundwork for future discoveries in prevention and treatment.
“As we approach this final stretch, it’s incredible to think about the journey we’ve all been on. The long hours, the countless visits families have made, and the deep relationships formed –all of it has been leading to this. We’re on the cusp of unlocking insights that could have a profound impact on preventing type 1 diabetes, and that’s incredibly exciting.”
Michael Killian
Director of Clinical Services
What Did We Learn?
TEDDY has already revealed important findings that are reshaping how we understand and approach T1D and related autoimmune conditions:
- Identified four key autoantibodies (IAA, GADA, IA-2A, ZnT8A) that signal the highest risk of progressing to T1D.
- Defined the Genetic Risk Score (GRS) now used globally to screen for risk of T1D and celiac disease.
- Found that 26% of TEDDY participants with certain gene combinations developed celiac disease autoimmunity (CDA) by age five: 12% progressed to full celiac disease.
- Showed that children born in spring and summer (March-August), had a 29% higher chance of developing celiac autoimmunity by age 10.
- Found higher rates of CD in Swedish participants compared to those in Germany, Finland, and the U.S.
TEDDY also showed that children identified as high risk could be monitored to reduce the chance of developing diabetic ketoacidosis—a dangerous complication at disease onset.
TEDDY has given us amazing insights into type 1 diabetes (T1D), and what the future of treatment and prevention can look like. With 64,000 new T1D diagnoses each year in the U.S. and 500,000 new cases worldwide, the more information we have, the better prepared we are to fight the disease.
Who is at Risk?
Genetics account for roughly half of the risk of developing T1D, and the ability to sequence an individual’s genome has revolutionized our understanding of who might be affected. Children with a family history of T1D are at higher risk–but surprisingly, nearly 85% of new diagnoses occur in families with no prior history.
That’s why studies like TEDDY are so important. They go beyond family trees to identify broader genetic risk patterns and examine how environmental triggers might activate those risks. TEDDY has helped define who is most at risk–and what early warning signs can be used to catch T1D before it becomes life-threatening.
“TEDDY didn’t just track data—it built a roadmap for how we might prevent autoimmune disease before it starts.”
Claire Cowen Crouch
Clinical Research Manager
Why TEDDY Matters
Rarely do we get such a detailed view into the earliest moments of a disease. TEDDY’s strength lies in its scale and depth: biological samples, home drinking water, baby teeth, diet logs, health records, and stressful life events–all collected regularly from over 8,500 children over 15 years.
TEDDY demonstrated that it’s possible to identify early signs of autoimmunity, predict disease before symptoms begin, and prevent life-threatening complications. These insights are now helping shape public health approaches to screening and early intervention.
What’s Next? The CASCADE Project
The next step in translating TEDDY’s discoveries into real-world solutions is the CASCADE Project–Combined Autoantibody Screening for Celiac and Diabetes Evaluation. Led by PNRI, CASCADE will analyze thousands of samples from the Washington’s Newborn Screening Program (NBS) over the next five years.
The goal: demonstrate that population-wide screening for T1D and CD is not only possible, but critical for prevention. The project will culminate in a recommendation to add T1D to the state’s newborn screening panel, helping to catch the disease before symptoms appear.
By identifying risk early, healthcare providers can take action before serious complications develop. CASCADE could transform how we detect and manage T1D–starting at birth.
At PNRI, science that improves lives is our passion. We are proud to collaborate with NBS on CASCADE, and excited about the future possibilities this project holds.
“With CASCADE, we’re shifting from reactive to proactive healthcare. Newborn screening for type 1 diabetes and celiac disease risk is helping us catch early signs and set the stage for timely intervention.”
Michael Killian
Director of Clinical Services
Meet the Team Behind TEDDY and CASCADE
Claire Cowen Crouch
Clinical Research Manager
Michael Killian
Director of Clinical Services
Margaret Marquiss
Laboratory Technician
Cody McCall
Clinical Coordinator
Arlene Meyer
Research Interviewer II
Jared Radtke
Senior Research Technician
Shreya Roy
Clinical Coordinator
Jennifer Skidmore
Senior Clinical Coordinator
Learn More About the TEDDY and CASCADE Studies
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