Diabetes Care, Vol 19, Issue 3 249-251, Copyright © 1996 by American Diabetes Association
Renal function in long-duration type I diabetes
P Mackin, JM Macleod, JP New and SM Marshall
Department of Medicine, University of Newcastle, Newcastle Upon Tyne, U.K.
OBJECTIVE: The development of persistent proteinuria is reported to be
uncommon after 30 years of type I diabetes, and the significance of
microalbuminuria in patients with long-duration diabetes is unclear. We
therefore undertook to study, in detail, renal function in patients with
long-duration type I diabetes. RESEARCH DESIGN AND METHODS: We measured
albumin excretion rate (AER), glomerular filtration rate (GFR), and serum
creatinine in 140 patients with > or = 30 years of type I diabetes. We
also assessed patients for other micro- macrovascular complications of
diabetes together with factors implicated in the development of diabetic
renal disease. RESULTS: Of the patients, 23% had microalbuminuria (AER
20-200 micrograms/min and/or urinary albumin-to-creatinine ratio [ACR] >
2.5 mg/mmol [men] or > 3.5 mg/mmol [women] and dipstick negative for
proteinuria), 4% had overt nephropathy (AER > 200 micrograms/min or
persistent dipstick positive proteinuria), and 73% were normoalbuminuric
(AER < 20 micrograms/min or ACR < 2.5 mg/mmol [men], < 3.5 mg/mmol
[women]). Patients with microalbuminuria had lower GFR (81.5 +/- 30.2 vs.
96.0 +/- 20.3 ml.min-1.1.73 m-2; P = 0.06) and higher serum creatinine (104
+/- 32 vs. 92 +/- 16 mumol/l; P = 0.06) than those patients with
normoalbuminuria. Both serum creatinine (P < 0.05) and tobacco
consumption (P = 0.01) were significantly and independently related to
elevated albumin excretion. CONCLUSIONS: A substantial proportion of these
patients have microalbuminuria and evidence of impaired renal function,
suggesting that progression to end-stage renal failure may still be
inevitable. Clinicians should continue to monitor renal function in these
patients. The relationship between tobacco consumption and nephropathy also
makes clear the need to reduce cigarette smoking in the diabetic
population.