A longitudinal assessment of the natural rate of decline in renal function with age.

Background: Cross-sectional studies have long suggested that renal function declines with age. Longitudinal studies regarding this issue are limited.

Methods: We retrospectively analyzed a database of subjects attending a screening center in Israel between the years 2000-2012. Only subjects with normal estimated glomerular filtration rate (eGFR) were included. eGFR was assessed consequently at 5 or more yearly visits. The rate of decline in GFR with age was assessed in healthy subjects and in subjects with comorbidities.

Results: The cohort included 2693 healthy subjects and 230 subjects with different comorbidities. Mean (±standard error) annual rate of decline in eGFR in healthy subjects was 0.97 ± 0.02 ml/min/year/1.73 m(2). This decline increased significantly from 0.82 ± 0.22 in age-group 20-30 years to 0.84 ± 0.08, 1.07 ± 0.08 and 1.15 ± 0.12 ml/min/year/1.73 m(2) in age groups 31-40, 41-50 and 50 years and older respectively (p < 0.001). No correlation was found between the annual decline in eGFR and body mass index. In subjects with hypertension, diabetes mellitus, impaired fasting glucose or combined comorbidity the decline in eGFR was 1.12 ± 0.12, 0.77 ± 0.16, 0.85 ± 0.17, and 1.18 ± 0.26 ml/min/year/1.73 m(2) respectively.

Conclusions: This large longitudinal study provides new data on the decrease in eGFR with age. Accurate prediction of the natural rate of GFR decline might be used to distinguish between normally aging kidneys and those with chronic disease. This approach could avoid unnecessary diagnostic procedures in the former and facilitate appropriate treatment in the latter.