Mild Albuminuria Is a Risk Factor for Faster GFR Decline in the Nondiabetic Population
AuthorMelsom, Toralf; Solbu, Marit Dahl; Schei, Jørgen; Stefansson, Vidar Tor Nyborg; Norvik, Jon Viljar; Jenssen, Trond Geir; Wilsgaard, Tom; Eriksen, Bjørn Odvar
Methods: In the Renal Iohexol Clearance Survey, we measured GFR using iohexol clearance in 1567 middle-aged nondiabetic individuals with an ACR <3.40 mg/mmol (30.0 mg/g) at baseline. The ACR was measured in unfrozen morning urine samples collected on 3 days before the GFR measurements. A total of 1278 (81%) participants had follow-up with GFR measurements after a median of 5.6 years.
Results: The median ACR at baseline was 0.22 mg/mmol (interquartile range: 0.10-0.51 mg/mmol), the mean ± SD GFR was 104.0 ± 20.1 ml/min, and the mean ± SD GFR decline rate was -0.95 ± 2.23 ml/min per year. Higher baseline ACR levels were associated with a steeper GFR decline in adjusted linear mixed models. Study participants with ACR levels of 0.11 to 0.45 and 0.46 ± 3.40 mg/mmol had a 0.25 ml/min per year (95% confidence interval [95% CI]: -0.03 to 0.53) and 0.31 ml/min per year (95% CI: 0.02-0.60) steeper rate of decline than those with ACR ≤0.10 mg/mmol in multivariable-adjusted analyses. Among study participants with an ACR of <1.13 mg/mmol (defined as the optimal range), those with an ACR of 0.11 to 1.12 mg/mmol (n = 812) had a 0.28 ml/min per year (95% CI: 0.04-0.52) steeper rate of GFR decline than those with an ACR of ≤0.10 mg/mmol (n = 655).
Conclusion: A mildly increased ACR is an independent risk factor for faster GFR decline in nondiabetic individuals.