Is the decline of renal function different before and after the start of dialysis?

The presence of glomerular filtration in dialysis patients is associated with improved survival and quality of life. This study explores the time course of the glomerular filtration rate (GFR) between 1 year before and 1 year after the start of haemodialysis (HD) and peritoneal dialysis (PD). This study included 1861 incident dialysis patients (NECOSAD cohort; 62% male, 60 ± 15 years, 61% HD, GFR 5.2 ± 3.6 mL/min/1.73 m(2)). A decline of the GFR was estimated using linear mixed-effects models adjusted for age, sex, primary kidney disease, cardiovascular disease and diabetes. The rate of decline was allowed to change at a certain point in time. The decline of the GFR attenuated from -0.53 mL/min/1.73 m(2)/month (95% CI: -0.58, -0.48) in the period before the start of dialysis to -0.12 (95% CI: -0.20, -0.04) at 2-4 months of dialysis in all patients. In HD, decline attenuated from -0.51 (95% CI: -0.57, -0.44) to -0.14 (95% CI: -0.26, -0.02); in PD from -0.55 (95% CI: -0.62, -0.48) to -0.11 (95% CI: -0.23, 0.01). In patients who started dialysis with a GFR equal/above median GFR at dialysis start, the decline attenuated (at 3 months) from -0.70 (95% CI: -0.78; -0.62) to -0.21 (95% CI: -0.36; -0.05). In patients who started dialysis with a GFR below median GFR at dialysis start, the decline attenuated (at 1 month) from -0.73 (95% CI: -0.88; -0.58) to -0.04 (95% CI: -0.27 , 0.19). The apparent decline of the GFR slows down after 2-4 months of dialysis. This decline was similar in HD and PD patients, although at a different level of GFR. Further studies are needed to examine explanations for this phenomenon