People who have concussions caused by sports activities are at risk of serious consequences, including repeated concussions and possibly permanent brain damage.
A concussion is a temporary change in brain function after a head injury without any signs of brain damage visible on imaging tests, such as computed tomography (CT) or magnetic resonance imaging (MRI).
Sports that involve high-speed collisions (for example, football, rugby, ice hockey, and lacrosse) have the highest rates of concussion, but few sports, including cheerleading, are free of risk. Almost 20% of contact sports participants have a concussion over the course of a season. Estimates of the number of sports-related concussions vary from 200,000 per year to 3.8 million per year. Estimates vary so much because getting an accurate count is difficult when people are not evaluated in a hospital.
Concussions probably do not occur more often in athletes than they have in the past, but they are being recognized more often. The increased recognition is because people are more aware that repeated concussions can have serious consequences.