Low-dose aspirin for primary and secondary prevention of cardiovascular events in Denmark 1998-2018

Randomised controlled trials have shown a neutral or even unfavourable risk-benefit balance of aspirin for primary prevention of cardiovascular events. Using Danish nationwide registries, we investigated aspirin use and associated risks during the past two decades (1998-2018). We linked individual patient data on repeated aspirin redemptions with registered hospital ICD-10 diagnoses of atherosclerotic cardiovascular disease and bleedings. The prevalence of aspirin use among 1.1 million Danish adults fluctuated over the 20-year study period peaking in 2008 with 8.5% (5.4% primary prevention) and dropping to 5.1% (3.1% primary prevention) in 2018. Aspirin use showed strong age dependency, and 21% of individuals>80 years were treated with aspirin for primary prevention in 2018. Medication adding to bleeding risk was used concurrently by 21% of all aspirin users in 2018. The incidence of major bleedings were similar with primary and secondary prevention aspirin use and highest in elderly (2 per 100 patient years among individuals>80 years in 2018). In conclusion, low-dose aspirin use for primary prevention of cardiovascular events remains prevalent. The widespread use of aspirin, especially among older adults, and substantial concomitant use of medications adding to bleeding risk warrant increased focus on discontinuation of inappropriate aspirin use.