Commonly used painkillers (NSAIDs) are used for the treatment of painful conditions, fever, and inflammation. They are among the most sold medicines in the world but have side effects such as ulcers and increased blood pressure. NSAIDs have now also been linked to heart problems such as heart attack, heart failure, and irregular heartbeat. It is therefore recommended to use NSAIDs with great care in patients with heart disease. This research project will use data from Danish registries to answer important questions on the safety of NSAIDs. It will examine types of NSAIDs not previously looked at and whether warnings from health authorities have influenced doctors’ prescribing of NSAIDs to heart patients. Scientists will also examine whether NSAIDs increase the risk of heart attack in persons with cardiovascular risk factors, such as diabetes, smoking, and obesity. Finally, the project will examine whether NSAID use results in larger heart attacks than in people not using these drugs.