Age and female sex are associated with a higher risk of stroke in atrial fibrillation (AF). We sought to determine whether advancing age and female sex are associated with higher atrial fibrosis.

We conducted an observational cohort study of patients with AF enrolled in the University of Utah AF Database and a non-AF control group who underwent late-gadolinium enhancement magnetic resonance imaging (LGE-MRI) for atrial fibrosis quantification. Participants with contra-indications for contrast MRI scanning were excluded. Nine hundred and eight consecutive men and women with AF and 15 non-AF controls were included in this study. Left atrial fibrosis increased with age in both men and women with AF. Women with AF (n = 316) were older than men (n = 592): mean age 68.7±11.6 vs. 64.9±11.7 years; P < 0.01, and had higher left atrial fibrosis compared with men 17.5 ± 10.1% vs. 15.3 ± 8.9%; P < 0.001. Women also had a higher prevalence of prior stroke compared with men (15.8% vs. 6.5%; P < 0.001). Age and sex relationships with atrial fibrosis remained significant in multivariate analysis. Compared with the non-AF control group, patients with AF had significantly higher atrial fibrosis: 16.0 ± 9.4 vs. 5.5 ± 5.8%; P < 0.001.

Advancing age and female sex are associated with a higher burden of atrial fibrosis in patients with AF. Women with a prior history of stroke also have higher fibrosis compared with both women and men without history of stroke. Advanced fibrosis may explain the female and age association with stroke in AF.