Optimal adherence threshold to non-vitamin K antagonist oral anticoagulants (NOACs) in patients with atrial fibrillation to reduce the risk of thromboembolism and death

Abstract

Abstract Background Poor adherence to non-vitamin K antagonist oral anticoagulants (NOACs) may raise thromboembolic risks in patients with atrial fibrillation (AF). However, the minimal adherence to maintain the protective effects of NOACs is currently unknown. Purpose To investigate thresholds of NOAC adherence in association with thromboembolic and mortality risks. Methods Using two Belgian nationwide healthcare databases, AF patients ≥45 years old with ≥1 NOAC prescription claim between January 1st, 2013 and January 1st, 2019 were identified. Patients were followed from NOAC initiation until the first occurrence of the investigated outcome, treatment discontinuation (>60-day supply gap), switch to VKAs, death, emigration or end of the study period. Adherence was measured using the proportion of days covered (PDC) after one year of treatment. Inverse probability weighted Cox regression (adjusting for 39 confounding covariates) was used to investigate outcomes (identified using International Classification of Diseases-coded hospital discharge diagnoses and medical procedure codes) between NOAC users with a one-year PDC of 100% (reference group) and NOAC users with lower PDCs. Results A total of 92,111 newly-treated AF patients were included during a mean follow-up of 2.7 ± 1.4 years (250,750 person-years of on-treatment follow-up). The proportions of persistent NOAC users with a PDC of 100%, 95-99%, 90-94%, 85-89%, 80-84% and <80% after one year of treatment were 62.7%, 17.4%, 9.5%, 5.1%, 2.8% and 2.5%, respectively. Compared to NOAC users with a one-year PDC of 100%, significantly higher risks of stroke or systemic embolism were observed among NOAC users with PDCs of 85-89% (adjusted hazard ratio (aHR) 1.35, 95% confidence interval (CI) (1.19-1.54)), 80-84% (aHR 1.31, 95%CI (1.08-1.58)) and <80% (aHR 1.64, 95%CI (1.34-2.01)), while no significant differences were observed among NOAC users with one-year PDCs of 95-99% (aHR 1.02, 95%CI (0.94-1.12)) or 90-94% (aHR 1.06, 95%CI (0.95-1.18)) after multivariable adjustment. Significantly higher risks of all-cause mortality (aHR 1.09, 95%CI (1.01-1.17) and major or clinically relevant non-major bleeding (aHR 1.10, 95%CI (1.04-1.16) were observed with decreasing levels of NOAC adherence, starting from NOAC users with a one-year PDC of 90-94% versus 100%. Findings were similar with once-daily and twice-daily dosed NOACs. Conclusion Lower adherence to NOAC treatment is associated with increased risks of thromboembolism, all-cause mortality and bleeding. For adequate stroke prevention in AF, the optimal adherence threshold to NOAC treatment should be at least 90%, irrespective of the dosing regimen of NOACs.Figure 1