RT Journal
A1 Guskiewicz KM, McCrea M, Marshall SW, et al
T1 Cumulative effects associated with recurrent concussion in collegiate football players: The ncaa concussion study
JF JAMA
JO JAMA
YR 2003
FD November 19
VO 290
IS 19
SP 2549
OP 2555
DO 10.1001/jama.290.19.2549
UL http://dx.doi.org/10.1001/jama.290.19.2549
AB Context 
                  Approximately 300 000 sport-related concussions occur annually
in the United States, and the likelihood of serious sequelae may increase
with repeated head injury.Objective 
                  To estimate the incidence of concussion and time to recovery after concussion
in collegiate football players.Design, Setting, and Participants 
                  Prospective cohort study of 2905 football players from 25 US colleges
were tested at preseason baseline in 1999, 2000, and 2001 on a variety of
measures and followed up prospectively to ascertain concussion occurrence.
Players injured with a concussion were monitored until their concussion symptoms
resolved and were followed up for repeat concussions until completion of their
collegiate football career or until the end of the 2001 football season.Main Outcome Measures 
                  Incidence of concussion and repeat concusion; type and duration of symptoms
and course of recovery among players who were injured with a concussion during
the seasons.Results 
                  During follow-up of 4251 player-seasons, 184 players (6.3%) had a concussion,
and 12 (6.5%) of these players had a repeat concussion within the same season.
There was an association between reported number of previous concussions and
likelihood of incident concussion. Players reporting a history of 3 or more
previous concussions were 3.0 (95% confidence interval, 1.6-5.6) times more
likely to have an incident concussion than players with no concussion history.
Headache was the most commonly reported symptom at the time of injury (85.2%),
and mean overall symptom duration was 82 hours. Slowed recovery was associated
with a history of multiple previous concussions (30.0% of those with ≥3
previous concussions had symptoms lasting >1 week compared with 14.6% of those
with 1 previous concussion). Of the 12 incident within-season repeat concussions,
11 (91.7%) occurred within 10 days of the first injury, and 9 (75.0%) occurred
within 7 days of the first injury.Conclusions 
                  Our study suggests that players with a history of previous concussions
are more likely to have future concussive injuries than those with no history;
1 in 15 players with a concussion may have additional concussions in the same
playing season; and previous concussions may be associated with slower recovery
of neurological function.