Of 14,635 high-school sports injuries reported during the 2008-10 school years, 1,936 (13.2 percent) were concussions, according to an epidemiological study published in January in the American Journal of Sports Medicine. This was nearly twice the rate reported in earlier studies of high-school athletes.
The increase isn't as great as it seems. The earlier studies didn't include boys' ice hockey and boys' lacrosse -- where the incidence of concussions is fairly high -- and one of the earlier studies didn't count concussions if the time the athlete lost from sports activity was less than a day.
Concussions in the 20 sports studied occurred most often as a result of player-to-player contact and were more than twice as likely to happen in competition than in practice, researchers at Nationwide Children's Hospital in Columbus, Ohio, found. The one exception was cheerleading. Cheerleaders were 10 times more likely to be hurt in practice than while performing at games or competing in cheerleading competitions.
Most of the concussions were mild. In 40 percent of cases, concussion symptoms disappeared within three days. A majority of athletes who suffered concussions returned to play within three weeks. About 25 percent returned to practice in a day. In 2 percent of cases, the athlete resumed play on the same day he or she suffered the injury.
"This improper practice was widespread," noted researchers Mallika Marar, Natalie McIlvain, Sarah Fields and R. Dawn Comstock, who found it in 12 of the 20 sports they studied. "This clearly violates the consensus statement on sports-related concussion, which recommends that no adolescent athlete who sustains a concussion should return to play on the day of the injury."
The practice is more than improper, said Anthony Kontos, assistant research director for the University of Pittsburgh Medical Center's Sports Medicine Concussion Program. It's against the law in many states.
Athletes who suffer a concussion should wait at least a week after becoming asymptomatic before returning to the sport, the researchers said.
"Any time there is a suspected concussion, it has to be automatic that the athlete is removed from competition or practice and is not returned until he or she is symptom-free at rest, have passed a baseline test and also have passed a test indicating the athlete is symptom-free after exertion," Dr. Kontos said.
The concussion symptoms most often reported were headache (94.2 percent), dizziness (75.6 percent) and concentration difficulty (54.8 percent).
About 11 percent of the athletes who suffered concussions had had concussions before. The incidence of recurrent concussions was highest in boys' wrestling (20 percent).
Because repeated concussions can result in serious brain injury, it is especially important in these cases to "err on the side of caution" before permitting the athlete to resume play, the researchers said.
By far the most concussions (47 percent of the total) were in football. Girls' soccer (8.2 percent) was second. The safest sport was boys' volleyball, where no concussions were reported. Concussions as a proportion of total injuries were highest in boys' ice hockey, girls' lacrosse and cheerleading.
The researchers measured the relative risk of concussions in the various sports by athlete exposure, which was defined as one athlete taking part in one athletic practice or competition.
Although most concussions were suffered by boys, "in all gender-comparable sports studied, girls had higher rates of concussions than boys, and concussions represented a greater proportion of all injuries in girls than in boys," the researchers said, a finding consistent with earlier studies.
Biomechanical differences in the head and neck may explain this disparity, the researchers said. But it may exist simply because "female athletes may generally be more honest about reporting injuries."
Most concussions were the result of athlete-to-athlete contact. Girls were more likely than boys to suffer concussions from contact with the playing surface and from contact with players' equipment. This was especially true in girls' lacrosse and field hockey.
Because of this, "referees should remain especially vigilant in sports that include sticks and fast-moving projectiles," the researchers said.
Some changes in rules and equipment might also be warranted, Kontos said. Male lacrosse players wear helmets, he noted, but female lacrosse players do not.
(Contact Jack Kelly: firstname.lastname@example.org.)
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