Differential Effects of Admission Hemoglobin A_1c by Estimated Glomerular Filtration Rate Stages on Mortality in Acute Ischemic Stroke and Diabetes

BACKGROUND: The relationship between admission hemoglobin A_1c (HbA_1c) levels, estimated glomerular filtration rate (eGFR) stages, and early outcomes may provide key insights into the need for individualized glycemic control based on kidney function in patients with ischemic stroke and diabetes. METHODS: We analyzed data from a multicenter, nationwide, prospective stroke registry in South Korea, including patients with ischemic stroke within 7days of onset and diabetes. Admission HbA_1c levels (prestroke glycemic status) were categorized as <6.0%, 6.0% to 7.0%, 7.0% to 8.0%, and ≥8.0%. eGFR stages were classified from stage 1 to stage 5 based on the Kidney Disease: Improving Global Outcomes 2021 guidelines. The primary outcome was 3-month all-cause mortality. Cox proportional hazards models were performed and an interaction term between eGFR stages and HbA_1c groups was included to evaluate potential effect modification. RESULTS: A total of 27496 patients (age, 69.6±11.4years; men, 60.3%) were included. The 3-month cumulative all-cause mortality rates differed significantly by admission HbA_1c levels: 8.9% in HbA_1c <6.0% versus 5.3% in HbA_1c ≥8.0%. In adjusted analyses, while no association between HbA_1c <6.0% and mortality was observed among eGFR stages, higher HbA_1c levels (7.0%–8.0% in eGFR stages 1, 3, and 5, and ≥8.0% in stages 2 and 5) were significantly associated with increased mortality risk. Notably, in stage 4, there was no significant association between HbA_1c and mortality (P=0.027 for interaction). CONCLUSIONS: The association between admission HbA_1c and 3-month mortality varied among eGFR stages. These findings suggest that eGFR stage may need to be considered when tailoring glycemic control strategies in patients with ischemic stroke and diabetes.