Diabetes is a leading cause of stroke, especially ischemic stroke. Patients with type 2 diabetes have an increased risk of stroke estimated to range from 150% to 400% compared with those without diabetes. The association between hemoglobin A1c (HbA1c) and stroke risk, along with its subtypes, is rarely reported. A recent study investigated the association between HbA1c and the risk of incident stroke in patients with type 2 diabetes based on real-world data from three healthcare systems.  This large health system-based cohort of 27,113 African Americans and 40,431 whites with T2D was completed over four years.  It was found that 7,735 patients developed stroke (6,862 ischemic and 873 hemorrhagic).  The results showed a U-shaped association, which showed that both lower HbA1c and higher HbA1c levels were associated with higher risks of incident stroke. The U-shaped curve was more pronounced among patients taking antidiabetic, lipid-lowering, and antihypertensive medications compared with those without these medications. In the analysis restricted to stroke cases only diagnosed by inpatient or emergency, the U-shape association appears more pronounced. These results indicate that both intensive and poor glycemic control might be associated with an increased risk of stroke in patients with type 2 diabetes. These data suggest that diabetes management may have to be individualized according to the guideline recommendations rather than intensively attempting to lower HbA1c. 

Comment from Dr. Richard K. Bernstein, publisher of “Diabetes Solution”:  

The possible reasons for the study showing a U-shaped curve are the fact they show that those in the lowest A1c group got the most medications, including antidiabetic, lipid-lowering, and antihypertensive medicines compared with those without these medications.  Also, the time frame was only 3yrs, not enough time to destine a person for stroke unless on an anticoagulant. It is often the case that type 2s with the lowest A1c get the most meds.  And there are several commonly used meds for diabetics that can cause strokes. 

Journal of Stroke 2020;22(1):87-98. Published online: January 31, 2020 

DOI: https://doi.org/10.5853/jos.2019.01704