Young age at diabetes diagnosis amplifies the effect of diabetes duration on risk of chronic kidney disease: a prospective cohort study.

AIMS/HYPOTHESIS: We postulated that the increased lifetime risk of chronic kidney disease (CKD) in young-onset diabetes is attributable to both long disease duration and more aggressive disease. We examined whether age at diabetes diagnosis modifies the effect of diabetes duration on risk of CKD. METHODS: We included 436,744 people with incident type 2 diabetes in the Hong Kong Diabetes Surveillance Database (HKDSD) and 16,979 people with prevalent type 2 diabetes in the Hong Kong Diabetes Register (HKDR). We used Poisson models to describe joint effects of age at diabetes diagnosis, diabetes duration and attained age on incidence of CKD in HKDSD. We used Cox proportional hazards models to examine interaction effect of age at diabetes diagnosis and diabetes duration on risk of CKD with adjustment for confounders in HKDR. RESULTS: During a median follow-up of 5.3 years, 134,043 cases of CKD were recorded in the HKDSD. The incidence rate ratio for CKD comparing people of the same attained age but diagnosed with diabetes at ages 5 years apart was higher for people with a younger age at diabetes diagnosis, but decreased with increasing age at diabetes diagnosis. During a median follow-up of 6.3 years, 6500 people developed CKD in the HKDR. The increased risk of CKD with longer diabetes duration decreased with older age at diabetes diagnosis. The adjusted HR for CKD associated with 5 year increase in diabetes duration was 1.37 (95% CI 1.13, 1.65) in people with diabetes diagnosed at 20-29 years and 1.01 (95% CI 0.87, 1.18) in those diagnosed at ≥70 years. CONCLUSIONS/INTERPRETATION: Young age at diabetes diagnosis amplified the effect of increasing diabetes duration on increased risk of CKD.