Mayo Clinic Radio: American Stroke Month May is American Stroke Month. According to the American Stroke Association, stroke is the nation’s No. 5 killer and a leading cause of long-term disability. The American Stroke Association’s statistics show, on average, someone in the U.S. has a stroke every 40 seconds, and every 4 minutes someone dies from one. A stroke occurs when the blood supply to part of the brain is interrupted or reduced, depriving brain tissue of oxygen and nutrients. Within minutes, brain cells begin to die. Prompt treatment is crucial to minimize brain damage and potential complications.