OP2-1 - Non-adherence to Direct Oral Anticoagulants among new users and old users in patients with atrial fibrillation in French clinical practice

Background: Direct oral anticoagulants (DOAC) are prescribed for stroke prevention in patients with atrial fibrillation. Their efficacy is directly dependent on strict adherence because of the rapid reversibility of its anticoagulant effect. Non- or low-adherence with DOAC has been associated with higher all-cause mortality, morbidity and increased risk of thromboembolic events. Few studies have compared non-adherence between new DOAC users and old users   although they may behave differently toward their medication because of the level of knowledge of their treatment and its benefits.

Objectives: To estimate nonadherence (i.e. not taking drugs as prescribed) to DOAC in new and old DOAC users and identify factors associated with nonadherence.

Methods: We used The Health Improvement Network (THIN) database in France which is referenced by the French health authorities. It contains anonymized data from Electronic Health Records in primary care from 1700 general practitioners and specialists as well as all dispensing data for drugs.

All adult patients with a diagnosis of non-valvular atrial fibrillation were included. Old users were users with a DOAC dispensed in 2017 and 2018, and non-adherence was evaluated in 2019. New users were followed for 1 year from their 1st DOAC dispensing in 2018.

Then, secondary non-adherence was measured by the proportion of days covered (PDC), and defined as PDC< 80% at 6 and 12 months and also as PDC< 90% at 6 and 12 months because the 90% adherence threshold for DOAC was shown to be associated with better clinical outcomes.

Finally, multivariate logistic regression was performed to assess factors associated with nonadherence in the 2 distinct populations.

Results: A total of 1358 new users and 3865 old users were included in the study. Among new users, the average age was 74.5±10.3 years and 55.4% were male. Among old users, the average age was 76.2±9.5 and 58.1% were male.

The proportion of non-adherent patients was higher among old users than among new users, regardless of the threshold applied (80% or 90%) or the duration of follow-up (at 6 months or 1 year). The overall proportion of patients with PDC< 80% was 33.0% in old users vs 19.7% in new users at 6 months and 39.7% for old users vs 29.5% for new users at 1 year.

The proportion of patients who had a PDC < 90% was 46.3% in old users vs. 28.1% in new users at 6 months and it was 53.3% in old users vs 38.6% in new users at 1 year. 

The results were similar for all types of DOAC. In multivariate analysis, the factors associated with non-adherence were age less than 65 years for both groups and a number of concomitant medications between 0 and 4 for old users.

Conclusions: Non-adherence was quite high and importantly, non-adherence was significantly higher in old users. Additional research to understand the reasons is needed.  Similar to previous studies, age < 65 years and a number of concomitant medications between 0 and 4 were associated with non-adherence.