The CDC has just released a new report entitled "Nonfatal Traumatic Brain Injuries Related to Sports and Recreation Activities Among Persons Aged ≤19 Years --- United States, 2001--2009." It provides a wealth of information on the topic and a number of references to other articles and resources. One of the key points is:
"From 2001 to 2009, the estimated number of sports and recreation--related TBI visits to emergency departments (EDs) increased from 153,375 to 248,418, and the estimated rate of TBI visits increased from 190 per 100,000 population to 298. The two most common sports and recreation activities associated with ED treatment for TBI were bicycling and playing football."
Check out the complete article on CDC's Website.