Introduction
Cardiovascular diseases (CVD) are responsible for nearly half of all deaths globally (1). Minimizing the impact of CVD and related disabilities is a major challenge and aspirin is the oldest and most reliable drug for this purpose (2). It is an indispensable drug in the secondary prevention of CVD (2). The net benefit is well established and supported by a large body of evidence for secondary prevention patients (3-5). However, there is no clear consensus on whom aspirin therapy is appropriate for the primary prevention of CVD.
The 2016 European Society of Cardiology (ESC) guidelines on CVD prevention did not recommend aspirin therapy in primary prevention due to increased risk of bleeding (6). While this recommendation includes both patients with and without diabetes mellitus (DM) in European guidelines, the American Diabetes Association (ADA) 2018 guidelines recommend aspirin therapy in patients with DM aged 50 years or older with at least one additional CVD risk factor, without increased risk of bleeding (7). In parallel, 2016 United States Preventative Services Task Force (USPTF) (8) and 2019 American College of Cardiology/ American Heart Association (ACC/AHA) guidelines on the primary prevention of CVD states that aspirin (75-100 mg/day) might be used in selected patients aged 40 to 70 who have high CVD risk but not increased bleeding risk (9).
Recently, three large-scale randomized controlled trials evaluated the use of aspirin in the primary prevention of CVD. These trials provided further evidence for the use of aspirin in primary prevention. The Aspirin in Reducing Events in the Elderly (ASPREE) trial enrolled elderly patients (10), the Aspirin to Reduce Risk of Initial Vascular Events (ARRIVE) trial enrolled patients with moderate to high CVD risk (11), and the A Study of Cardiovascular Events iN Diabetes (ASCEND) trial enrolled patients with DM (12). While ARRIVE and ASPREE trials showed no benefit in terms of CVD risk reduction, only the ASCEND trial indicated a lower rate of major CV events, but this effect was attenuated by a higher rate of major bleeding. There was no all-cause mortality benefit in these trials (9-11). However, indications, prescription patterns, and appropriateness of aspirin use have not been well investigated with randomized or observational studies in Turkey. Therefore, the Appropriateness of Aspirin Use in Medical Outpatients: A Multicenter, Observational Study (ASSOS) aims to investigate the potential misuse of aspirin in both primary and secondary prevention patients. The ASSOS is the largest multicenter domestic trial regarding this topic. The use of aspirin therapy was evaluated taking into account the risk of CVD and bleeding in this real-world trial.