The TEDDY Study Turns 20: A New Era for T1D Insights

Over the past quarter century, advances in genome sequencing have revolutionized science and medicine, including how we understand complex diseases like type 1 diabetes (T1D). By identifying genetic markers linked to susceptibility to disease, researchers have been able to uncover new insights into how genetics and the environment interact to influence health.

This progress underpins PNRI’s work with the TEDDY Study, a pioneering international research effort to determine the environmental triggers that contribute to T1D. 

With National Diabetes Awareness Month in November and TEDDY’s 20th anniversary in 2024, it’s the perfect time to share how this groundbreaking study is expanding our understanding of T1D.

What is the TEDDY Study?

TEDDY – short for The Environmental Determinants of Diabetes in the Young – is a first-of-its-kind international research project. Its goal is to uncover environmental factors that may trigger autoimmunity and T1D. PNRI has proudly been a part of TEDDY from the start, serving as the only TEDDY research center on the West Coast, in addition to leading initiatives and committees central to the study.  

TEDDY researchers investigate a wide range of factors, including infectious agents, diet, environmental exposures, and psychosocial factors, to determine their role in T1D development. This work has led to groundbreaking discoveries about the disease, with much more to come as data analysis continues.

“TEDDY is the longest-running project in diabetes research,” says Michael Killian, Director of Clinical Services at PNRI. “It’s a testament to the families who’ve committed years of their lives to helping us understand this complex disease.”

Who’s at Risk for T1D?

Genetics play a significant role, accounting for at least half the risk of developing T1D. While the disease often runs in families, nearly 85% of new cases occur in individuals with no immediate family history. This highlights the importance of broader screening beyond hereditary ties. However, genetics alone doesn’t determine disease onset. Most people with genetic risk factors never develop T1D, which raises questions about the role of diet, environmental exposures, and life events.

Michael emphasizes that one of TEDDY’s strengths is its holistic approach: “By studying how genetics and the environment interact, we’re unraveling the complexities of what truly drives type 1 diabetes—and finding ways to act earlier.”

What Did TEDDY Researchers Study?

Over two decades, TEDDY researchers worked with more than 8,500 children and their families across the globe, collecting over 850,000 biological samples—including blood, urine, stool, toenails, baby teeth, and even samples of home drinking water.

Families joined the study when their children were as young as three months old and participated for 15 years, creating a long-term dataset that is unmatched in scope and depth. Beyond sample collection, researchers interviewed families to track diet, overall health, stressful life events, and other environmental factors to understand how these elements might influence T1D risk. This level of commitment provided researchers with a wealth of information to investigate how genetics and the environment interact to influence the onset of T1D.

TEDDY scientists also focused on autoantibodies—proteins that mistakenly attack the body as if it were a foreign invader. They identified autoantibodies most strongly associated with T1D, helping researchers and clinicians better predict a child’s risk of developing the disease. These findings are essential for earlier intervention and future prevention strategies.

What Did We Find Out?

So much! 

TEDDY’s research has led to groundbreaking discoveries, including:

Autoantibodies and T1D Risk: Researchers identified four key autoantibodies—IAA, GADA, IA-2A, and ZnT8A—that significantly increase the risk of T1D. This knowledge improves disease prediction.

Genetic Risk Score (GRS): TEDDY scientists developed the GRS to identify genetic factors that increase the risk of T1D and celiac disease. This tool is now used worldwide to pinpoint individuals who may benefit from additional medical screening.

T1D and Celiac Disease Connections: TEDDY explored the link between T1D and celiac disease (CD) and found that 26% of participants with certain genetic traits developed celiac disease autoimmunity (CDA) by age 5, with 12% progressing to full CD.

Season of Birth and Risk: The study found that children born in spring and summer (March–August) have a 29% higher risk of developing CDA by age 10, showing how seemingly unrelated factors may influence disease.

Geographic Differences: Swedish participants were more likely to develop celiac disease than children in Germany, Finland, or the U.S., highlighting the value of global collaboration.

Why This Matters

These discoveries are just the beginning. TEDDY is transforming how scientists approach T1D, offering hope for better treatments and, ultimately, prevention.

As Michael explains, “Prevention is the ultimate goal—not only to reduce the burden on individuals and their families but to make a societal impact. If we can prevent T1D, healthcare resources can be directed elsewhere, benefiting everyone.”

By understanding the triggers and mechanisms behind T1D, researchers are laying the foundation for solutions that could stop the disease before it starts. While TEDDY has already deepened our knowledge of T1D and celiac disease, continued analysis of its vast data set will fuel future breakthroughs.

With 64,000 new T1D diagnoses each year in the U.S. and 500,000 globally, every discovery moves us closer to combating this disease effectively.

Learn More

To learn more about this exciting work, check out our recent Q&A with TEDDY researchers Bill Hagopian, MD, PhD, and Michael Killian. You can also listen to episode 3 of our podcast, PNRI Science: Mystery and Discovery, in which PNRI CEO Jack Faris sits down with Bill and Michael to get their perspective on future of T1D research.