Background: The role of glycemic control and its variability on the rate of kidney function decline after the onset of diabetic kidney disease (DKD) remains unclear.
Methods: The association between baseline HbA1c and rates of estimated GFR (eGFR) loss during follow-up was examined by mixed-effects linear regression in 530 individuals with type 1 diabetes and early-to-moderate DKD from the Preventing Early Renal Loss (PERL) trial, and 2,378 individuals with type 2 diabetes and established DKD from the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial. The benefit of intensive vs. standard glycemic control in slowing eGFR decline was examined in ACCORD. The associations between continuous glucose monitoring-derived short-term glycemic variability indices and rate of GFR decline were also evaluated in PERL.
Results: A higher baseline HbA1c was associated with a more negative eGFR slope in both PERL and ACCORD (-0.87 and -0.27 ml/min/1.73m2/year per Hba1c unit increment, p<0.0001 and p=0.0002, respectively). In both studies, the strength of this association progressively increased with increasing levels of albuminuria (p for interaction <0.05). Consistent with this, the benefit of intensive glycemic control on eGFR decline was greater in ACCORD participants with severe than in those with moderate albuminuria (+1.13 vs. +0.26 ml/min/1.73 m2/year, p=0.01). No independent associations were found in PERL between short-term glycemic variability indices and rate of eGFR decline.
Conclusions: In both type 1 and type 2 diabetes, poor glycemic control is associated with a more rapid rate of GFR decline after DKD onset, especially in persons with severe albuminuria.
Keywords: Diabetic kidney disease; glycemic control; kidney function decline.
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