A small, prospective study of 40 retired National Football League (U.S.) players revealed over 40% had MRI evidence of traumatic brain injury. Additionally, these individuals experienced significant abnormalities in attention and concentration (42%), in executive functions (50%), and learning/memory issues (44.7%). Excellent resources about sports concussions are available here.
PositiveTip: Growing evidence suggests caution before allowing children or adults to engage in contact sports.