East Asian immigration and direct oral anticoagulant dosing for atrial fibrillation: A population-based cohort study.

Background: Some East Asian (EA) guidelines recommend lower doses of direct oral anticoagulants (DOACs) for atrial fibrillation (AF) than in North America and Europe.

Objective: Investigate the association of immigration from EA with DOAC dosing and outcomes in AF.

Methods: Population-based cohort study using administrative databases of Ontario immigrants with AF aged ≥66 years who were dispensed DOAC prescriptions from 2012-2019. Birth country was classified as EA or not. We used multivariable logistic regression to assess the association of EA birth with DOAC dose and cause-specific hazards regression for the association of EA birth and DOAC dose with stroke/bleeding/death. Interaction between EA birth and DOAC dosing was studied for each outcome.

Results: Among 14,421 immigrants, 3958 (27.4%) were born in EA. EA immigrants had lower odds of receiving full-dose DOACs versus non-EA immigrants (OR 0.64, 95%CI 0.58-0.69, p<0.001). EA birth was not associated with a composite of hospitalization for stroke/bleeding (HR 0.97, 95%CI 0.84-1.12, p= 0.67) nor hospitalization for stroke (HR 0.86, 95%CI 0.71-1.04, p= 0.13), but was associated with higher bleeding hazard (HR 1.15, 95%CI 1.02-1.30, p= 0.02) and lower mortality (HR 0.91, 95%CI 0.84-0.99, p= 0.04). There was no significant interaction between EA birth and DOAC dosing for stroke (p=0.41), bleeding (p=0.27), or death (p=0.33).

Conclusions: EA immigrants were less likely to receive full-dose DOACs and had a higher bleeding hazard, similar stroke hazard, and lower mortality risk than non-EA immigrants. There was no evidence that DOAC dosing had a differential treatment effect in EA immigrants.