Proton pump inhibitors are a widely-prescribed and popular over-the-counter choice of treatment for heartburn. In previous research PPIs have been associated with impaired vascular function, including heart attacks, kidney disease and dementia. This study investigates whether PPIs are also associated with ischemic stroke, which is the most common form of stroke in which a blood clot cuts off the flow of blood to the brain. The research, conducted in Denmark, finds little increased stroke risk for very low doses. However, at higher dosages stroke risk increased 33% for Prilosec and Prevacid patients, 50% for Nexium patients and 79% for Protonix patients.