Antiplatelet therapy use for the secondary prevention of cardiovascular disease in 2009–2017: a population-wide retrospective cohort study of Scotland
Authors: Thalmann I , Preiss D , Schlackow I , Gray A , Mihaylova B 
Published: October 2022

Abstract

Background
Few studies have analysed the adequacy of antiplatelet therapy (APT) use for secondary prevention of atherosclerotic cardiovascular disease (ASCVD). Some studies found utilisation to be suboptimal. However, information on the extent of APT use at different treatment stages and over time, and the role of particular individual characteristics, is limited.

Purpose
To use large-scale population-wide individual patient data to investigate the extent of, and determinants for, suboptimal use of effective APT, in order to identify patient groups that could be targeted to improve medication use.

Methods
This retrospective open cohort study used anonymised large-scale population-wide individual patient NHS Scotland data (hospital admissions, national death records, prescribing information and speciality mental health admissions) for all individuals hospitalised for ASCVD (based on ICD-10 discharge codes) in Scotland between 1 October 2009 and 31 December 2017. APT initiation was defined as a prescription of APT within 90 days of ASCVD hospital discharge with dispensing within 60 days of the prescription. Adherence was defined as ≥80% of days covered with dispensed therapy. Discontinuation of APT was defined as a treatment gap of 180 days or more since initiation. Multivariable cross-sectional logistic regression and Cox proportional hazards models were used to study the relevance of patient characteristics (e.g., demographic, clinical, socioeconomic) to the likelihood of, respectively, initiating or discontinuing APT. Findings are reported for all ASCVD events and, separately, for myocardial infarction (MI), ischaemic stroke, peripheral arterial disease (PAD) and other ASCVD events.

Results
Of 150,728 individuals hospitalised for ASCVD (excluding any diagnosis of atrial fibrillation), 16% did not initiate any APT. Initiation was less common in women (22% less likely than men), people aged ≥70 or &lt;50 (21% and 39% less likely for patients in their 70s and 80s respectively vs. 60s; 26% less likely for patients below age 50 vs. 60s), people living in more deprived areas, people receiving specialist mental health care and people with multiple morbidities (Figure). There was substantial variation for lack of initiation across ASCVD types (e.g., MI 6%, PAD: 32%). In 2015/17, 72% of MI patients and 69% of patients undergoing percutaneous coronary intervention received guideline-recommended dual-APT. While on treatment, 93% of users were adherent. However, about a quarter (23%) discontinued treatment. Similar characteristics linked to lack of initiation of APT were associated with an increased risk of discontinuation.

Conclusions
APT initiation and persistence remain suboptimal, especially in women, people aged below 50 years and 70 years or older, people with multiple morbidities or mental illness, and following non-MI ASCVD events. This needs to be addressed by clinicians and policy-makers to further reduce cardiovascular risk.

Funding Acknowledgement
Type of funding sources: Public Institution(s). Main funding source(s): Oxford British Heart Foundation Centre of Research Excellence (BHF CRE) Pump Priming Scheme; Medical Research Council Doctoral Training Programme (MRC DTP) studentship.