Low risk of overt nephropathy after 24 yr of childhood-onset type 1 diabetes mellitus (T1DM) in Norway

Abstract

AIM: To estimate the risk of diabetic nephropathy and associated risk factors in a nationwide cohort of childhood-onset type 1 diabetes mellitus (T1DM) and 19-30 yr of diabetes duration. METHODS: Patients diagnosed with childhood-onset T1DM (<15 yr) from 1973 through 1982, who previously (1989-1990) participated in a clinical examination to assess diabetic complications, were invited for a new examination in 2002-2003. Of 355 eligible patients, 299 participated (84.2%), and complete urine samples for evaluation of albuminuria were obtained from 295 patients, with a mean age of 33 yr (range 20.9-44.0) and mean diabetes duration of 24 yr (range 19.3-29.9). Persistent microalbuminuria and overt nephropathy [albumin excretion rate (AER) 15-200 microg/min and AER > 200 microg/min, respectively] in at least two out of three consecutive overnight urine samples were defined as diabetic nephropathy. RESULTS: Overt nephropathy was found in 7.8% [95% confidence interval (CI) 4.7-10.9] and persistent microalbuminuria in 14.9% (95% CI 10.8-19.0) of the subjects. Hemoglobin A1c (HbA1c) (p = 0.001), systolic blood pressure (BP) (p = 0.002), total cholesterol (p = 0.019), and C-reactive protein (CRP) (p = 0.019) were associated with diabetic nephropathy. Significant predictors in 1989-1990 for the development of diabetic nephropathy in 2002-2003 were HbA1c (p < 0.001), AER (p = 0.007), and cholesterol (p = 0.022). CONCLUSIONS: In a subgroup of patients diagnosed with childhood-onset T1DM in 1973-1982, 7.8% had overt nephropathy after 19-30 yr of diabetes duration, which is low compared with studies from other countries. HbA1c, systolic BP, total cholesterol, and CRP were each independently associated with diabetic nephropathy.