Relation of Hemoglobin A1C Levels to Risk of Ischemic Stroke and Mortality in Patients With Diabetes Mellitus and Atrial Fibrillation

Diabetes mellitus (DM) is associated with an increased risk of complications in atrial fibrillation (AF). This study aimed to assess the incidence and risks of ischemic stroke and mortality according to baseline HbA1c levels in patients with DM and AF. We conducted a cohort study using Clalit Health Services electronic medical records. The study population included all Clalit Health Services members aged ≥25 years, with the first diagnosis of AF between January 1, 2010, and December 31, 2016, who had a diagnosis of DM. The risk of stroke and all-cause death were compared according to HbA1c levels at the time of AF diagnosis: <7.0%, between 7% and 9%, and ≥9%. A total of 44,451 patients with DM and AF were identified. The median age was 75 years (interquartile 65 to 83), and 52.5% were women. During a mean follow-up of 38 months, higher levels of HbA1c were associated with an increased risk of stroke with a dose-dependent response when compared with patients with HbA1c <7% (Adjusted hazard ratio [aHR] =1.30 [95% confidence interval 1.10 to 2.05] for levels between 7% and 9% and 1.60 (95% confidence interval 1.25 to 2.03) for HbA1c >9%, even after adjusting for CHA₂DS₂-Vasc risk factors and use of oral anticoagulants. The risk for overall mortality was significantly higher in the HBA1C >9% group (aHR = 1.17 [1.07 to 1.28]). In conclusion, in this cohort of patients with AF and DM, HbA1c levels were associated with the risk of stroke in a dose-dependent manner even after accounting for other recognized risk factors for stroke.