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Hemoglobin a1c levels and the risk of ischemic stroke and mortality in individuals with diabetes mellitus and atrial fibrillation

Pfizer Israel

Diabetes mellitus (DM) is associated with increased risk of embolic complications in non-valvular atrial fibrillation (NVAF). Whether the risk of stroke in AF patients remains the same among the wide spectrum of disease is yet to be determined.

Among individuals with AF and DM, to assess the incidence rates and risk of ischemic stroke and mortality by baseline HbA1C levels.

We conducted a prospective, historical cohort study using the Clalit Health Services (CHS) electronic medical records database. The study population included all CHS members ≥ 21 years old, with a first diagnosis of NVAF between January 1, 2010 to December 31, 2016 and a minimal follow-up period of 1 year. Among those patients identified as diabetics, we compared three groups of patients according to HBA1C levels at the time of AF diagnosis: <7.0%, between 7-9% and ≥ 9%.

A total of 44,451 cases were identified. The median age was 75 years (IQR 65-83) and 52.5% were women. During a mean follow up of 38 months, the incidence of stroke per 100 person-years in the three study groups was: 1.9 in patients with HBA1C <7%, 2.37 in the intermediary group and 2.72 in those with HBA1C >9%. In both univariate and multivariate analyses, higher levels of HBA1C were associated with an increased risk of stroke compared with a dose-dependent response when compared to individuals with HBA1C <7% (Adjusted Hazard Ratio (AHR) = 1.32 {95% CI 1.12-1.55}for levels between 7-9% and AHR 1.64 {95% CI 1.28-2.09}) even after adjusting for CHA2DS2-VASC individual risk factors and use of oral anti-coagulants. The risk for overall mortality did not differ significantly between groups, with a slight elevation in the HBA1C >9% group after adjusted analysis {aHR = 1.17 (1.07- 1.28)} Conclusion: In this observational cohort of patients with incident newly diagnosed nonvalvular atrial fibrillation, HBA1C levels were associated with an increased risk of stroke in a dose-dependent manner even after accounting for other recognized risk factors for stroke in this population.

Abstract Figure. Kaplan-Meier for stroke-free survival