Exploring the relationship between adherence and outcomes in pulmonary arterial hypertension: A retrospective cohort study in the United States

BACKGROUND: Pulmonary arterial hypertension (PAH) is a rare, progressive disease with significant morbidity and mortality. New medications have improved outcomes, but adherence is crucial. OBJECTIVE: Exploring adherence to PAH-specific therapies across therapeutic classes, we identified factors associated with non-adherence and evaluated its impact on clinical outcomes. METHODS: Using claims from the Komodo Research Database, we identified patients initiating therapy with phosphodiesterase type 5 inhibitors (PDE5i), endothelin receptor antagonists (ERA), soluble guanylate cyclase (sGC) stimulators, or prostacyclin pathway agents (PPA) between January 2017 and June 2022. Adherence was measured by proportion of days covered (PDC) during the treatment period, defined as 60 days after first therapy until treatment discontinuation/censor. Non-adherence was defined as PDC 90 %); non-adherence was highest with PDE5i (17.0 %) and inhaled PPA (15.3 %). Factors associated with non-adherence varied by drug class. Non-adherence was significantly associated with worse clinical outcomes: in the PDE5i group, risk of mortality more than doubled with non-adherence (HR 2.33 [95 % CI 1.79-3.03]; p < 0.001), and increased more than fivefold in the ERA group (5.43 [3.33-8.85]; p < 0.001). CONCLUSIONS: Non-adherence to PAH therapy is associated with poor clinical outcomes. Strategies to improve adherence are crucial to optimizing patient outcomes.