The association between influenza infection, vaccination, and atrial fibrillation: A nationwide case-control study

Background Influenza infection could activate systemic inflammatory responses and increase the sympathetic tone that plays an important role in the pathogenesis of atrial fibrillation (AF). Objectives The goal of the present study was to investigate whether influenza infection was a risk factor for AF. We also aimed to study whether influenza vaccination could decrease the risk of AF. Methods From 2000 to 2010, a total of 11,374 patients with newly diagnosed AF were identified from the Taiwan National Health Insurance Research Database. On the same date of enrollment, 4 control patients (without AF) with matched age and sex were selected to be the control group for each study patient. The relationship between AF and influenza infection or vaccination 1 year before the enrollment was analyzed. Results Compared with patients without influenza infection or vaccination (reference group; n = 38,353), patients with influenza infection without vaccination (n = 1369) were associated with a significantly higher risk of AF with an odds ratio of 1.182 (P =.032) after adjustment for baseline differences. The risk of AF was lower in patients receiving influenza vaccination without influenza infection (n = 16,452) with an odds ratio of 0.881 (P <.001). In patients who have received influenza vaccination and experienced influenza infection (n = 696), the risk of AF was similar to that in the reference group (odds ratio 1.136; P =.214). The lower risk of AF with vaccination was consistently observed in subgroup analyses. Conclusion Influenza infection was significantly associated with the development of AF, with an 18% increase in the risk, which could be reduced through influenza vaccination.