It's a long tail.
It is surprising that long term studies haven't been done before: one more indication that there is much to learn about "mild" TBI.
Concussion's Effects May Linger for DecadesAANS - Facts about concussion.
WEDNESDAY, Jan. 28 (HealthDay News) -- Athletes who suffer a concussion can experience a decline in their mental and physical processes more than 30 years later, according to a Canadian study that's the first to identify these kinds of long-term effects.
The researchers examined 40 healthy, former university-level athletes between the ages of 50 and 60. Of those, 19 had suffered a concussion more than 30 years ago, and 21 had no history of concussion.
Compared to those who were concussion-free, the participants who'd been concussed only once or twice in their early adulthood showed declines in attention and memory, as well as a slowing of some types of movement.
Most research focuses on the immediate, post-concussion period and on deciding when it's safe for a concussed athlete to return to play. The long-term effects of concussion tend to be overlooked.
CDC - Facts for Physicians about Mild TBI
Report to Congress on Mild TBI (2003)
GAO - Report on Mild TBI Screening for Veterans (2008)