UCSF

Background

Diagnosed diabetes mellitus (DM) is a consistently documented risk factor for ischemic stroke in patients with atrial fibrillation (AF).

Objectives

The purpose of this study was to assess the association between duration of diabetes and elevated hemoglobin A1c (HbA1c) with risk of stroke among diabetic patients with AF.

Methods

We assessed this association in the ATRIA (Anticoagulation and Risk Factors in Atrial Fibrillation) California community-based cohort of AF patients (study years 1996 to 2003) where all events were clinician adjudicated. We used Cox proportional hazards regression to estimate the rate of ischemic stroke in diabetic patients according to time-varying measures of estimated duration of diabetes (≥3 years compared with <3 years) and HbA1c values (≥9.0% and 7.0% to 8.9% compared with <7.0%), focusing on periods where patients were not anticoagulated.

Results

There were 2,101 diabetic patients included in the duration analysis: 40% with duration <3 years and 60% with duration ≥3 years at baseline. Among 1,933 diabetic patients included in the HbA1c analysis, 46% had HbA1c <7.0%, 36% between 7.0% and 8.9%, and 19% ≥9.0% at baseline. Duration of diabetes ≥3 years was associated with an increased rate of ischemic stroke compared with duration <3 years (adjusted hazard ratio [HR]: 1.74, 95% confidence interval [CI]: 1.10 to 2.76). The increased stroke rate was observed in older (age ≥75 years) and younger (age <75 years) individuals. Neither poor glycemic control (HbA1c ≥9.0%, adjusted HR: 1.04, 95% CI: 0.57 to 1.92) nor moderately increased HbA1c (7.0% to 8.9%, adjusted HR: 1.21, 95% CI: 0.77 to 1.91) were significantly associated with an increased rate of ischemic stroke compared with patients who had HbA1c <7.0%.

Conclusions

Duration of diabetes is a more important predictor of ischemic stroke than glycemic control in patients who have diabetes and AF.