The epidemiology of atrial fibrillation in adults depends on locale of diagnosis.

BACKGROUND

Previous studies on atrial fibrillation (AF) epidemiology have used various case definitions for AF, but the effect of location of diagnosis on the apparent epidemiology of AF is unknown.

METHODS

Population-based study of 46,440 consecutive patients with newly diagnosed AF in Alberta, Canada, from 2000 to 2005.

RESULTS

Of adults newly diagnosed with AF (52.8% men, median 73 years), 51.8% were first diagnosed in hospital, 19.2% in emergency department (ED), and 29.0% in outpatient clinics. Prevalence of AF increased from 613 per 100,000 to 1,148 per 100,000 population over 5 years; however, the age- and sex-standardized incidence of AF remained relatively stable (350 per 100,000 in 2000 and 352 per 100,000 in 2005). The proportion of AF cases diagnosed in hospital declined 21% between 2000 and 2005, whereas the proportion of cases diagnosed in the outpatient setting rose by 50% (P < .0001). Patients diagnosed with AF in the hospital or the ED had more comorbidities and higher CHADS(2) (congestive heart failure, hypertension, age ≥75 years, diabetes mellitus, and prior stroke or transient ischemic attack) scores than those diagnosed in the outpatient setting (all P < .0001). Multivariate adjusted risk of cerebrovascular events or mortality (adjusted odds ratios 4.3, 95% CI 3.9-4.7) was significant for hospital and ED AF diagnosis (adjusted odds ratios 2.4, 95% CI 2.2-2.7) compared with those diagnosed in primary care clinics. New heart failure in the year after diagnosis of AF was 4.5% for inpatients, 3.8% in ED patients, and 2.5% in outpatients.

CONCLUSIONS

Use of hospitalizations alone to define an AF cohort may underestimate incidence while overestimating comorbiditities, thromboembolic risk, and outcomes.