Cumulative Concussions

Cumulative or repetitive concussion is most widely studied in the world of sports medicine. Researchers investigating the relationship between blast exposure and concussion are currently looking to see if findings from sports medicine can be translated to the military population.

A National Collegiate Athletic Association (NCAA) football study (Guskiewicz et al.) found an association between the number of reported prior concussions in NCAA football players and the likelihood of sustaining another concussion. The study found that players reporting more than 3 prior concussions were three times more likely to sustain another concussion than players who reported no prior concussions. Among players reporting 2 prior concussions they were 2.5 times more likely to sustain another concussion. Players that reported only 1 prior concussion were 1.4 times more likely to sustain another concussion. The study also found that a prior history of concussion may be associated with slower recovery of neurological function. After a concussion, players most commonly complained of headache, dizziness/balance difficulties and feeling cognitively “slowed down.” Players who have sustained prior concussions should be educated regarding their increased risk of repeat concussions when continuing to play contact sports. This same study also suggested that a history of concussion is associated with prolonged recovery following future concussions.

A worst-case scenario is a rare complication called "second-impact syndrome" caused by sustaining a second concussion before the symptoms of the prior concussion have resolved. This condition can be fatal.

There is conflicting data regarding the cumulative pathologic effects of multiple concussions. There is also no consensus on how many concussions are too many, in either the sports world or The Military.

REFERENCES

Guskiewicz KM, McCrea M, Marshall SW, Cantu RC, Randolph C, Barr W, Onate JA, Kelly JP. (2003). Cumulative Effects Associated With Recurrent Concussion in Collegiate Football Players: The NCAA concussion study. JAMA 290: 2549-2555. [abstract] [full text]

Kelly JP, Nichols JS, Filley CM, Lillehie KO, Rubinstein D, Kleinschmidt-DeMasters BK: Concussion in Sports: Guidelines for the Prevention of Catastrophic Outcome. JAMA 1991; 266(20): 2867-2869. [abstract] [full text]