Impact of adherence to drugs for secondary prevention on mortality and cardiovascular morbidity: A population-based cohort study. IMPACT study

Purpose Adherence to pharmacological therapy for secondary prevention after an acute coronary syndrome (ACS) reduces the risk of new cardiovascular events. However, several studies showed poor adherence. Our study aim was to assess the risk of a composite endpoint of major cardiovascular events (MACE) and all-cause mortality according to the adherence to these drugs in patients after an ACS in a primary health care cohort. Methods Population-based observational cohort study of patients with a first episode of ACS during 2009-2016. Data source: Information System for Research in Primary Care (SIDIAP) database. Drug adherence was evaluated through proportion of days covered (PDC). Results We included 7152 patients and 5692 (79.6%) were adherent (PDC >= 75%) to the study drugs during the first year after the event. Adherents to any combination showed a significant reduction of the composite endpoint risk (HR 0.80 [0.73-0.88]), and a significant lower probability of the composite endpoint than nonadherents for all drugs, except beta-blockers. Adherents to 2 (HR 1.2; 95% CI 1.0-1.3) and 1 drug (HR 1.5; 95% CI 1.2-1.8) had higher composite endpoint risk compared to adherents to 4-3 drugs. Conclusion Adherence to any combination of recommended drugs reduced the composite endpoint risk, regardless the number of drugs prescribed. Adherence to a combination of 4-3 drugs was significantly associated with a reduced mortality risk compared with adherents to 2 or 1, but it was not significant for MACE.