“We were surprised to find that American Indians experienced a higher risk of atrial fibrillation, compared to every other racial and ethnic group,” Dr. Marcus said in a press release that accompanied the study. “Understanding the mechanisms and factors by which American Indians experience this higher risk may help investigators better understand the fundamental causes of atrial fibrillation that prove useful to everyone at risk for AFib, regardless of their race or ethnicity.”
The team plumbed the Healthcare Cost and Utilization Project (HCUP) California state databases for information on more than 16 million cases of AFib that occurred during 2005-2011. Native Americans comprised just 0.6% of the cohort. Most of the patients (57.2%) were white; 8% were black, 25.6% Hispanic, and 8.6% Asian. After targeting only new-onset cases, there were 344,469 incident AFib episodes over a median follow-up of 4.1 years.
The overall incidence of AFib in Native Americans was 7.49 per 1,000 person-years, significantly higher than the 6.89 per 1000 person-years observed in the rest of the cohort ( P
In an interaction analysis, the increased risk appeared to be driven by higher rates of diabetes and chronic kidney disease, the authors wrote.
“This may suggest that the presence of these two processes contributes some pathophysiology related to AF[ib] risk that may be similar to the heightened risk inherent among American Indians,” they wrote. “It is also important to note that there was no evidence of any other statistically significant interactions despite the inclusion of millions of patients.”
Supporting data for these associations were not included in the research letter.
The authors noted some limitations of their study. Race or ethnicity were self-reported and could not be independently confirmed, so there was no way to tease out the effects in multiracial patients. Also, the database didn’t record outpatient encounters, which might result in some selection bias.
“Last, because this was an observational study, these results should not be interpreted as evidence of causal effect,” they noted.
“In conclusion, we observed that American Indians had a higher risk of atrial fibrillation, compared with all other racial and ethnic group. The heightened risk … in American Indians persisted after multivariable adjustment for known conventional confounders and mediators, suggesting that an unidentified characteristic, including possible genetic or environmental factors, may be responsible,” the investigators wrote.
The HCUP database is supported by the Agency for Healthcare Research and Quality. Dr. Marcus reported receiving research support from Jawbone, Medtronic, Eight, and Baylis Medical, and is a consultant for and holds equity in InCarda Therapeutics. The other authors reported no conflicts of interest.