More than two million Americans and more than four million people in the European Union have paroxysmal or persistent atrial fibrillation.1 Its prevalence increases dramatically with advancing age, rising from 0.1% in adults younger than 55 years to 9.0% in those aged 80 or more.2 Atrial fibrillation is associated with an increased long term risk of stroke, heart failure, and death. The healthcare costs related to this condition are substantial, largely as a result of hospital admissions, consultations, diagnostic and therapeutic procedures, and drug treatments. Many patients with atrial fibrillation need lifelong treatment with oral anticoagulants for stroke prevention, which requires careful dosing and laboratory monitoring; safety concerns about the risk of bleeding persist for these patients even under the most ideal systems of care. For these reasons, any opportunity to reduce the risk of atrial fibrillation, particularly in older adults, would be welcome. In the linked case-control study (doi:10.1136/bmj.d3450), Schmidt and colleagues describe an association between the use of non-selective non-steroidal anti-inflammatory drugs (NSAIDs) or selective cyclo-oxygenase-2 (COX 2) inhibitors …