Impact of onset age of type 2 diabetes mellitus on risk of renal complications compared to age‐matched non‐diabetic patients: Two cohort studies in the United Kingdom and Hong Kong

Abstract Objective With the increasing incidence of early‐onset type 2 diabetes mellitus (T2DM) and the significant burden of renal complications in younger patients, this study aimed to investigate the association between the age at onset of T2DM and the risks of renal complications. Methods Two retrospective cohort studies were conducted among adults without chronic kidney disease (CKD) from 2008 to 2013, utilising electronic health records from the United Kingdom (UK) and Hong Kong (HK). A total of 124 610 and 183 114 patients newly diagnosed with T2DM were included in the T2DM group, and 4 968 819 and 3 290 862 individuals without diabetes were included in the comparison group for the UK and HK cohorts, respectively. Participants were categorised into six age groups at baseline (18–39, 40–49, 50–59, 60–69, 70–79, and ≥ 80 years). Propensity score fine stratification weights were applied within each age group, and Cox regression analyses were performed to evaluate the association between T2DM and the risks of renal complications, including CKD, renal decline, and end‐stage renal disease (ESRD). Results Over a median followup of 11.6 years (approximately 57 million person‐years) in the UK cohort and 9.7 years (approximately 35 million person‐years) in the HK cohort, T2DM was associated with an increased risk of CKD, renal decline, and ESRD. However, the risks decreased with increasing age at T2DM onset. In the UK cohort, the hazard ratios (HRs) 95% confidence intervals (CIs) for the three outcomes among individuals with T2DM onset at 18–39 years versus those without diabetes were 1.87 (1.65, 2.11), 4.87 (4.38, 5.40), and 4.49 (3.03, 6.68), respectively. For individuals with T2DM onset at ≥80 years, the HRs decreased to 1.26 (1.21, 1.32), 1.66 (1.55, 1.78), and 1.48 (1.12, 1.96), respectively. A similar trend was observed in the HK cohort, with risks for all outcomes decreasing as the age of T2DM onset increased. Conclusion Early‐onset T2DM is associated with substantially higher risks of CKD, renal decline, and ESRD, underscoring the need for targeted prevention and management strategies to reduce renal complications in younger patients with T2DM.