Marginal structural models to evaluate the association between adherence to direct oral anticoagulants and safety or efficacy outcomes among patients with atrial fibrillation.

BACKGROUND

Although the management of atrial fibrillation (AF) has improved over the years, suboptimal adherence to direct oral anticoagulants (DOACs) is a major health concern. Adherence and long-term persistence to DOACs decline over time resulting in increased risks of stroke, major bleeding, and death.

OBJECTIVE

This study aimed to evaluate the association between adherence to DOACs and composite or bleeding events using marginal structural models (MSMs).

METHODS

A retrospective study was conducted using the Medicare Advantage Plan from January 2016 to December 2020. Patients with AF prescribed any DOACs were identified. Adherence was calculated using the proportion of days covered (PDC). Patients with PDC ≥ 0.80 were considered adherent. Composite (stroke, systemic embolism, acute coronary syndrome) and bleeding (major and minor) events were calculated for each of the 4 time periods. An MSM was conducted to estimate the association between adherence and composite efficacy or bleeding events by controlling for time-dependent covariates and time-dependent exposure affected by the previous exposure.

RESULTS

A total of 1969 patients with AF were included in the study. Adherence was suboptimal during all the 5 time periods, and it ranged from 39.8% to 53.12%. This study did not find any significant association between adherence to DOACs and composite efficacy or bleeding events. The safety and efficacy outcomes were comparable among apixaban, rivaroxaban, and dabigatran.

CONCLUSION

This study revealed that adherence declined over time among old patients with AF. Future studies should explore the association between adherence to DOACs and health outcomes for a longer duration of follow-up using MSM.