A narrative review of what cohorts have taught us and how they have laid the foundation for much of our understanding of type 2 diabetes – published online 26/08/2026

Sun H. Kim, Ipsa Arora, Charles Agyemang, Ranjit M. Anjana, Bjørn Olav Åsvold, Marieke Blom, Shilpa N. Bhupathiraju, Amélie Bonnefond, Juliana C. N. Chan, Timothy M. E. Davis, Kristian Hveem, Marit E. Jørgensen, Anton Lager, Lars Lind, Olle Melander, Andrea Natali, Jackie Price, Parminder Raina, Michael Roden, Olov Rolandsson, Mary R. Rooney, Seyed Mohammad Mousavi, Andrei C. Sposito, Reimar W. Thomsen, Barbara Thorand, Rob M. Van Dam, Kavita Venkataraman, Sarah H. Wild, Ji Hee Yu, Petra J. M. Elders, Joline W. Beulens, Femke Rutters

Cohort studies conducted over the past five decades have been central to redefining our understanding of type 2 diabetes, from early detection to long-term complications. In this issue, Kim et al (https://doi.org/10.1007/s00125-026-06812-4) describe how population-based and disease-based cohorts have uncovered the high percentage of those with undiagnosed diabetes, informed diagnostic thresholds (including HbA_1c), and clarified the burden and timing of microvascular and macrovascular, oncologic, cognitive, mental health and other comorbidities. The authors synthesise evidence on biological, lifestyle, psychosocial and socioeconomic determinants and show how cohorts have illuminated heterogeneity in pathophysiology across populations and life stages. The review also outlines emerging directions, including precision health, multi-omics, exposome research, registry-based ‘real‑world’ cohorts and hybrid observational–interventional designs. The authors conclude that together, these studies provide indispensable, complementary evidence to randomised trials and form a foundation for future guidelines, policies and targeted interventions to prevent and manage type 2 diabetes worldwide.