By Laura Cowen
Black individuals with atrial fibrillation (AF) have markedly higher rates of stroke, heart failure, coronary heart disease (CHD) and mortality than their White counterparts, data from the Atherosclerosis Risk in Communities (ARIC) study show.
These findings "have important public health implications", say Jared Magnani (University of Pittsburgh, Pennsylvania, USA) and co-authors.
These include an urgent "need to bolster prevention of adverse outcomes in black individuals with AF", as well as improving AF prevention in Black individuals overall in order to avoid the high social and medical costs of the associated morbidity, they say.
During a mean follow-up period of 20.6 years, Magnani and team identified 2348 cases of incident AF in 15,080 participants (mean age 54.2 years; 55% women; 25% Black individuals) of the ARIC study.
And although the incidence of AF was higher in White individuals than Black individuals, at 8.1 versus 5.8 cases per 1000 person-years, the rates of stroke, heart failure, CHD and mortality were higher in Black than White individuals, whether they had AF or not.
To assess the impact of AF on the absolute risk of each of these outcomes, the researchers calculated the rate difference per 1000 person-years between those with and without AF.
For stroke, the rate difference was 10.2 in White individuals and 21.4 in Black individuals. It was 71.8 and 101.4, respectively, for heart failure, and 25.6 and 44.9, respectively, for CHD. For all-cause mortality, White individuals had a rate difference of 55.9 compared with 106.0 for Black individuals.
This indicates "that black ARIC Study participants with AF are at considerably greater risk for associated adverse outcomes than white individuals with AF", Magnani and co-authors remark in JAMA Cardiology.
A second JAMA Cardiology study, published at the same time, used data on more than 17,000 people to investigate whether genetic variants account for racial differences in the risk of AF.
Gregory Marcus (University of California, San Francisco, USA) and colleagues identified one single nucleotide polymorphism (SNP) that accounted for between 11% and 32% of the reduced AF risk among Black individuals compared with White individuals.
Since this proportion was "modest", and no other SNPs were identified by genome-wide admixture mapping, Marcus et al suggest that "additional genetic or environmental influences beyond single SNPs in isolation may account for the paradoxical racial risk of AF among white individuals and black individuals."
Editorialists Thomas Stamos and Dawood Darber, from the University of Illinois at Chicago, USA, say that both studies "highlight the need for additional investigation regarding the possible social, environmental, and genetic causes for [their] findings."
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JAMA Cardiol 2016; Advance online publication