Gender-related differences in risk of cardiovascular morbidity and all-cause mortality in patients hospitalized with incident atrial fibrillation without concomitant diseases: a nationwide cohort study of 9519 patients

Background: Previous studies of patients with "lone" and "idiopathic" atrial fibrillation (AF) have provided conflicting evidence concerning the development, management and prognosis of this condition.

Methods: In this nation-wide, retrospective, cohort study, we studied patients diagnosed with incidental AF recorded in national Swedish registries between 1995 and 2008. Controls were matched for age, sex and calendar year of the diagnosis of AF in patients. All subjects were free of any in-hospital diagnosis from 1987 and until patients were diagnosed with AF and also free of any diagnosis within one year from the time of inclusion. Follow-up continued until 2009. We identified 9519 patients (31% women) and 12,468 matched controls.

Results: Relative risks (RR) versus controls for stroke or transient ischemic attack (TIA) in women were 19.6, 4.4, 3.4 and 2.5 in the age categories <55, 55-64, 65-74 and 75-85, years respectively. Corresponding figures for men were 3.4, 2.5, 1.7 and 1.9. RR for heart failure were 6.6, 6.6, 6.3 and 3.8 in women and 7.8, 4.6, 4.9 and 2.9 in men. All RR were statistically significant with p < 0.01. RR for myocardial infarction and all-cause mortality were statistically significantly increased only in the two oldest age categories in women and 65-74 years in men.

Conclusions: Patients with AF and no co-morbidities at inclusion had at least a doubled risk of stroke or TIA and a tripled risk of heart failure, through all age categories, as compared to controls. Women were at higher RR of stroke or TIA than men.