Long-Term Medication Adherence Trajectories to Direct Oral Anticoagulants and Clinical Outcomes in Patients With Atrial Fibrillation

Background Direct oral anticoagulants (DOACs) are widely used in patients with nonvalvular atrial fibrillation for stroke prevention. However, long-term adherence to DOACs and clinical outcomes in real-world clinical practice is not well understood. This study evaluated long-term medication adherence patterns to DOAC therapy and clinical outcomes in a large US integrated health care system. Methods and Results We included adult patients with nonvalvular atrial fibrillation who newly initiated DOACs between 2012 and 2018 in Kaiser Permanente Southern California. Long-term (3.5 years) adherence trajectories to DOAC were investigated using monthly proportion of days covered and group-based trajectory models. Factors associated with long-term adherence trajectories were investigated. Multivariable Poisson regression analyses were used to investigate thromboembolism and major bleeding events associated with long-term adherence trajectories. Of 18 920 patients newly initiating DOACs, we identified 3 DOAC adherence trajectories: consistently adherent (85.2%), early discontinuation within 6 months (10.6%), and gradually declining adherence (4.2%). Predictors such as lower CHA(2)DS(2)-VASc (0-1 versus >= 5) and previous injurious falls were associated with both early discontinuation and gradually declining adherence trajectories. Early discontinuation of DOAC therapy was associated with a higher risk of thromboembolism (rate ratio, 1.40; 95% CI, 1.05-1.86) especially after 12 months from DOAC initiation but a lower risk of major bleed compared with consistent adherence (rate ratio, 0.48; 95% CI, 0.30-0.75), specifically during the first 12 months following DOAC initiation. A gradual decline in adherence to DOACs was not statistically significantly associated with thromboembolism outcomes compared with consistent adherence. Conclusions Although a large proportion of patients with nonvalvular atrial fibrillation were adherent to DOAC therapy over 3.5 years, early discontinuation of DOAC was associated a higher risk of thromboembolic events. Future tailored interventions for early discontinuers may improve clinical outcomes.