Complication development trajectories for patients with type 2 diabetes mellitus: evidence from a five-million retrospective cohort study.

Background: Type 2 diabetes mellitus (T2DM) is a growing health burden in China. High complication rates contribute to increased morbidity, mortality, and costs. However, evidence is limited regarding how these complications develop and cluster over time in real-world settings, which this study examined. Methods: This retrospective cohort study used big data from the Cheeloo Lifespan Electronic Health Research Data Library, comprising data from over 5 million individuals in Shandong Province, China, to investigate the trajectories, onset timing and key risk factors of T2DM-related complications. Results: The prevalence of T2DM-related complications increased from 30.4% in 2013 to 53.1% in 2023. The median time from diagnosis to the first complication was 7.5 years. Ophthalmic, neurological, and circulatory complications were among the most common and showed the largest relative increases in prevalence over the study period. Complication profiles exacerbated over time: most patients developed multiple complications by Year 9. Frequent follow-up visits (≥4 times/year) and using primary health care (PHC) services were significantly associated with a reduced risk of complications, whereas being unmarried, being overweight, being obese, alcohol use, and poor medication adherence were significantly associated with a higher risk. Conclusion: Patients with T2DM in China face a substantial and growing burden of complications, with most developing multiple complications within ten years of diagnosis. Follow-up visits, the use of PHC services, and regular medication adherence are potential protective factors to prevent or delay the development of complication. These findings highlight the importance of integrated, community-based, and personalized management strategies to improve outcomes in T2DM populations.