QJM Advance Access originally published online on August 12, 2006
QJM 2006 99(9):595-599; doi:10.1093/qjmed/hcl075
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Age-related differences in renal function at onset of renal replacement therapy in chronic kidney disease stage 5 patients
From the Divisions of 1Geriatrics and 2Nephrology, Department of Internal Medicine, University of Virginia Health System, Charlottesville, USA
Address correspondence to Dr S.A. Balogun, Division of Geriatrics, Department of Internal Medicine, University of Virginia Health System, PO Box 800506, Charlottesville, VA 22908–0506, USA. email: sab2s{at}virginia.edu
Received 31 May 2005 and in revised form 8 May 2006
Background: Guidelines for initiating renal replacement therapy (RRT) are based on renal function and not age, so renal function at onset of RRT is expected to be similar across age groups.
Aim: To evaluate renal function at initiation of RRT across age groups.
Design: Observational cross-sectional study.
Methods: We extracted data for all incident chronic kidney disease (CKD) stage 5 patients (n = 322 064) commenced on chronic dialysis (haemodialysis and peritoneal) and renal transplant in the US from 1995 to 1999 from the US Renal Data Systems (USRDS). Subjects (n = 662) with incomplete data were excluded. The reminder (n = 321 402) were classified into five age groups: 0–19 years; 20–44 years; 45–64 years; 65–74 years; 
75 years. Mean values of serum creatinine (Cr, mg/dl), creatinine clearance (CrCl, ml/min), body weight (kg) and body mass index (BMI, kg/m2) at onset of RRT were computed. Mean daily urinary creatinine excretion per kg body weight (CrCl x Cr/0.07/weight) was also calculated.
Results: Progressively lower serum creatinine levels were found in adult patients with increasing age (10.70, 8.56, 7.38 and 6.88 mg/dl in those aged 20–44 years, 45–64 years, 65–74 years, 75 years, respectively). CrCl was also lower in the same groups (14.76, 13.38, 11.63 and 11.60 ml/min, respectively).
Discussion: Older patients have a greater reduction in renal function than younger patients at onset of RRT, suggesting a delay in initiation of therapy.