Daily aspirin found to increase the risk of heart attacks by 190%.
There is no scientific evidence to prove that daily aspirin increases the risk of heart attacks or myocardial infarction.
A number of websites have published claims that the risk of heart attacks is almost doubled in patients taking aspirin. These claims are based on a paper published earlier this year in the British Journal of Clinical Pharmacology (1).
The study was carried out by a group of Dutch researchers who interrogated the Clinical Practice Research Datalink. This is the world’s largest primary care database and consists of 674 primary care practices in the UK. The study population consisted of 30,146 patients who were aged 18 years of age and over. The primary aim of the study was to evaluate the risk of acute myocardial infarction in patients who were exposed to either vitamin K antagonists (coumarin) or new directly acting oral anticoagulants (rivaroxaban) or low-dose aspirin(<325 mg per day). The study did not look at the general population but focused on people with a heart arrhythmia or electrical disturbance known as atrial fibrillation.
The main study outcome was the finding that the risk of acute myocardial infarction in people with atrial fibrillation was doubled in patients receiving the new directly acting oral anticoagulants as compared to older agents such as coumarin. The study also noted a 190% increased incidence of acute myocardial infarction in patients with atrial fibrillation who were receiving aspirin monotherapy as compared with coumarin.
There are a number of problems with interpreting these data and simply assuming that aspirin increases the risk of heart attacks. Firstly, the patient population in this study all had atrial fibrillation and are not representative of the general population. Secondly, this is a population cohort study which means that the original selection of the oral anticoagulation was not randomized which introduces a significant bias into the study. In effect this means that there may have been patient difference that prompted the physician to choose one agent over another. This means that the differences between the drugs may not be due to the drugs but due to differences in the patients who took the drugs. Thirdly, this study only proves an association. This means that there is an association between aspirin use and acute myocardial infarction. This in no way proves that aspirin itself is responsible for the higher risk or that aspirin causes acute myocardial infarction.
In summary, there is no data to support this claim and it is misleading to suggest that aspirin increases the risk of heart attacks.
- Risk of myocardial infarction in patients with atrial fibrillation using vitamin K antagonists, aspirin or direct acting oral anticoagulants. Stolk LM, de Vries F, Ebbelaar C, de Boer A, Schalekamp T, Souverein P, Ten Cate-Hoek A, Burden AM. Br J Clin Pharmacol. 2017 Mar 22. doi: 10.1111/bcp.13264. [Epub ahead of print]