Clinical findings regarding the association between hemoglobin A1c (HbA1c) and stroke risk remain inconclusive, especially among patients with diabetes. We aimed to investigate the association between HbA1c and the risk of incident stroke in patients with type 2 diabetes using electronic medical record data from three large healthcare systems in Louisiana. We performed a retrospective cohort study of 27,113 African Americans and 40,431 whites with type 2 diabetes. Cox proportional hazards regression models were used to estimate the association of different levels of HbA1c with stroke risk. During a mean follow-up period of 3.74 years, 8986 patients developed stroke (8438 ischemic and 548 hemorrhagic). Multivariable-adjusted hazard ratios across levels of HbA1c at baseline (<6.0, 6.0-6.9 [reference group], 7.0-7.9, 8.0-8.9, 9.0-9.9, and ≥10%) were 1.05, 1.00, 1.13, 1.21, 1.24, and 1.35 (Ptrend <0.001) for total stroke, 1.04, 1.00, 1.13, 1.21, 1.24, and 1.35 (Ptrend <0.001) for ischemic stroke, and 1.26, 1.00, 1.10, 1.26, 1.22, and 1.40 (Ptrend =0.284) for hemorrhagic stroke. When we used an updated mean value of HbA1c, the U-shaped association of HbA1c with stroke risk did not change. This U-shaped association was consistent among patients of different age, race, sex, body mass index, never and past or current smokers. The U-shaped association was more pronounced among patients taking antidiabetic, lipid-lowering and anti-hypertensive medications compared with those without these medications. In the U-shaped association between HbA1c and the risk of total, ischemic and hemorrhagic stroke among patients with type 2 diabetes, the lowest risk was found among patients with HbA1c at 6-7 mmol/L.
Y. Shen: None. L. Shi: None. E. Nauman: None. P. Katzmarzyk: None. E.G. Price-Haywood: None. A.N. Bazzano: None. S. Nigam: None. G. Hu: None.
Patient-Centered Outcomes Research Institute (NEN-1508-32257); National Institute of General Medical Sciences (U54GM104940 to G.H., P.K.)