Microalbuminuria prevalence varies with age, sex, and puberty in children with type 1 diabetes followed from diagnosis in a longitudinal study

OBJECTIVE - The predictive value of microalbuminuria (MA) in children with type 1 diabetes has not been defined. We describe the natural history of MA in a large cohort of children recruited at diagnosis of type 1 diabetes. RESEARCH DESIGN AND METHODS - Between 1985 and 1996, 514 children (279 male ) who developed type 1 diabetes before the age of 16 years (91% of those el igible from a region where ascertainment of new cases is 95%) were recruite d for a longitudinal study with central annual assessment of HbA(1c) and al bumin excretion (three urine samples). Dropout rates have been <1% per year , and 287 children have been followed for >4.5 years. RESULTS - MA (defined as albumin-to-creatinine ratio greater than or equal to 3.5 and greater than or equal to 4.0 mg/mmol in boys and girls, respecti vely) developed in 63 (12.8%) and was persistent in 22 (4.8%) of the subjec ts. The cumulative probability (based on the Kaplan-Meier method) for devel oping MA was 40% after 11 years. HbA(1c) was worse in those who developed M K than in others (mean difference +/- SEM: 1.1% +/- 0.2, P < 0.001). In sub jects who had been 5-11 years of age when their diabetes was diagnosed, the appearance of MA was delayed until puberty, whereas of those whose age was <5 years at diagnosis of diabetes, 5 of 11 (45%) developed MA before puber ty. The adjusted proportional probability (Cox model) of MPI was greater fo r female subjects (200%), after pubertal onset (310%), and with greater HbA (1c) (36% increase for every 1% increase in HbA(1c)). Despite earlier diffe rences based on age at diagnosis of diabetes (<5, 5-11, and >11 years), the overall cumulative risks in these groups were similar (38 vs. 29 vs. 39%, respectively) after 10 years' duration of diabetes. CONCLUSIONS - Prepubertal duration of diabetes and prepubertal hyperglycemi a contribute to the risk of postpubertal MA. The differences in rates of de velopment of MA relating to HbA(1c), sex, and age at diagnosis relative to puberty may have long-term consequences for the risk of subsequent nephropa thy and for cardiovascular risk.