Female sex as a risk factor for stroke in atrial fibrillation: a nationwide cohort study
Article first published online: 4 SEP 2012
© 2012 International Society on Thrombosis and Haemostasis
Journal of Thrombosis and Haemostasis
Volume 10, Issue 9, pages 1745–1751, September 2012
How to Cite
MIKKELSEN, A. P., LINDHARDSEN, J., LIP, G. Y. H., GISLASON, G. H., TORP-PEDERSEN, C. and OLESEN, J. B. (2012), Female sex as a risk factor for stroke in atrial fibrillation: a nationwide cohort study. Journal of Thrombosis and Haemostasis, 10: 1745–1751. doi: 10.1111/j.1538-7836.2012.04853.x
- Issue published online: 4 SEP 2012
- Article first published online: 4 SEP 2012
- Accepted manuscript online: 14 JUL 2012 10:22AM EST
- Received 19 April 2012, accepted 6 July 2012
- atrial fibrillation;
- female sex;
Summary. Background: Female sex has been suggested as a risk factor for stroke/thromboembolism in patients with non-valvular atrial fibrillation (AF) and has therefore been included within risk scores, e.g. the CHA2DS2-VASc score, and guidelines.
Objectives: To investigate the risk of stroke/thromboembolism associated with female sex in non-valvular AF patients.
Patients/Methods: Using the national Danish registers, we identified non-anticoagulated patients discharged with non-valvular AF (1997–2008), and subdivided the population into three age intervals: < 65, 65–74 and ≥ 75 years. We calculated stroke rates according to sex, and assessed the stroke risk associated with female sex by using Cox regression analysis.
Results: We included 87 202 AF patients, and 44 744 (51.3%) were female. The rate of stroke/thromboembolism for females aged < 65 and 65–74 years was not increased as compared with men, whereas the rate for females aged ≥ 75 years was increased. At both 1-year and 12-year follow-up, female sex did not increase the risk of stroke for patients aged < 75 years. At 1-year follow-up, the hazard ratios associated with female sex were 0.89 (95% confidence interval [CI] 0.70–1.13) and 0.91 (95 CI 0.79–1.05) for patients aged < 65 and 65–74 years, respectively, and being female and aged ≥ 75 years was associated with an increased risk of stroke of 1.20 (95 CI 1.12–1.28).
Conclusion: Female sex was only associated with an increased risk of stroke for AF patients aged ≥ 75 years. Our study suggests that female sex should not be automatically included as an independent stroke/thromboembolic risk factor in guidelines or in the CHA2DS2-VASc score, without careful prior consideration of the ‘age < 65 and lone AF’ criterion.