Incidence of atrial fibrillation in whites and African-Americans: the Atherosclerosis Risk in Communities (ARIC) study

Abstract

Objectives: To define the incidence and cumulative risk of atrial fibrillation (AF) in a population-based cohort of whites and African Americans.

Background: African-Americans reportedly have a lower risk of AF than whites despite their higher exposure to AF risk factors. However, precise estimates of AF incidence in African Americans have not been previously published.

Methods: We studied the incidence of AF in the Atherosclerosis Risk in Communities (ARIC) study, which has followed up 15,792 men and women 45 to 65 years of age at baseline from 4 communities in the United States since 1987. Atrial fibrillation cases were identified from electrocardiograms conducted at baseline and 3 follow-up visits, and from hospitalizations and death certificates through the end of 2004. During follow-up, 1,085 new cases of AF were identified (196 in African Americans, 889 in whites).

Results: Crude incidence rates of AF were 6.7, 4.0, 3.9, and 3.0 per 1,000 persons per year in white men, white women, African-American men, and African-American women, respectively. Increasing age was exponentially associated with an elevated risk of AF. Compared to whites, African-Americans had a 41% (95% CI: 8%-62%) lower age- and sex-adjusted risk of being diagnosed with AF. The cumulative risk of AF at 80 years of age was 21% in white men, 17% in white women, and 11% in African-American men and women.

Conclusion: In this population-based cohort, African Americans presented a lower risk of AF than whites. Still, the burden of AF among the former is substantial, with 1 in 9 receiving a diagnosis of AF before 80 years of age.

Figure 1

Age- and sex-specific incidence rates of atrial fibrillation (AF) in population-based studies in the United States. Rates for the Cardiovascular Health Study include both whites and African-Americans; their race-specific rates have not been published.

Figure 2

Age-specific incidence rates of atrial fibrillation (AF) by study period, Atherosclerosis Risk in Communities Study, 1987-2004. Rates are standardized to the overall gender and race distribution in the study sample.

Figure 3

Cumulative risk of atrial fibrillation (AF) at selected index ages for race- and sex-specific groups, with death free of AF considered a competing event. Lifetime risk for a given index age is cumulative risk through age 80 years, Atherosclerosis Risk in Communities Study, 1987-2004.