Geographic Disparities in the Incidence of Stroke among Patients with Atrial Fibrillation in the United States

Aim: To determine whether regional variation in stroke incidence exists among individuals with AF. Methods: Using healthcare utilization claims from 2 large US databases, MarketScan (2007-2014) and Optum Clinformatics (2009-2015), and the 2010 US population as the standard, we estimated age-, sex-, race- (only in Optum) standardized stroke incidence rates by the 9 US census divisions. We also used Poisson regression to examine incidence rate ratios (IRR) of stroke and the probability of anticoagulation prescription fills across divisions. Results: Both databases combined included 970,683 patients with AF who experienced 15,543 strokes, with a mean follow-up of 23 months. In MarketScan, the age-and sex-standardized stroke incidence rate was highest in the Middle Atlantic and East South Central divisions at 3.8/1000 person-years (PY) and lowest in the West North Central at 3.2/1000 PY. The IRR of stroke and the probability of anticoagulation fills were similar across divisions. In Optum Clinformatics, the age-, sex-, and race-standardized stroke incidence rate was highest in the East North Central division at 5.0/1000 PY and lowest in the New England division at 3.3/1000 PY. IRR of stroke and the probability of anticoagulation fills differed across divisions when compared to New England. Conclusions: These findings suggest regional differences in stroke incidence among AF patients follow a pattern that differs from the hypothesized trend found in the general population and that other factors may be responsible for this new pattern. Cross-database differences provide a cautionary tale for the identification of regional variation using health claims data.