Athletes with a history of concussion are at risk of suffering lasting symptoms the next time they take a blow to the head, according to a study published Monday.

On the other hand, the study authors found, these athletes appear less likely than those suffering a first concussion to report more-immediate symptoms-suggesting, the researchers say, that some may keep their problems to themselves so they can get back in the game.

Suspicion should be raised, the investigators report in the journal Neurology, when an “eager” athlete claims to be symptom-free soon after suffering a concussion.

A concussion occurs when a jolt to the head jostles the brain within the skull, sometimes tearing nerve fibers. Symptoms that emerge within minutes to hours of the injury may include headache, dizziness, disorientation and nausea. Longer-term problems, which may crop up days or weeks after the injury, include chronic headache, poor concentration, memory loss and sleep disturbances.

Research has shown that athletes with a history of concussion are at greater risk of suffering a repeat injury, and if that second concussion happens soon after the first, the effects can be severe.

The new study, according to the authors, reinforces experts’ advice that athletes not return to play until concussion symptoms fully subside - and that those with previous head injuries should take extra time to recover.

According to the American Academy of Neurology, an athlete who has had multiple concussions should stay out of the game for a week or more, depending on the severity of the new injury.

For the current study, Jared M. Bruce, then a grad student at Pennsylvania State University in University Park, and Dr. Ruben J. Echemendia followed 433 male college athletes in a variety of sports.

During the study period, 57 athletes sustained a concussion, 30 of whom had suffered such an injury before. All were given tests of neurological function and were asked to report any symptoms at two hours, two days and one week after the injury.

The researchers found that two hours after being injured, athletes with no history of concussion reported more symptoms than did those who had suffered a Head injury in the past. A week later, however, athletes with repeat concussions were four times more likely than first-timers to report problems with thinking or coordination - 32 percent versus 8 percent.

The fact that athletes with a previous concussion reported fewer immediate symptoms could indicate that they are “less distressed” by early concussion symptoms than their less-experienced peers are, according to Bruce and Echemendia.

However, they add, the finding could also mean that these athletes are more likely to cover up symptoms because they know a concussion will sideline them for a time.

The study, according to an accompanying commentary, offers several messages for coaches, parents and doctors - one being that repeat concussions should be treated as potentially serious and given extended healing time.

Another, the authors add, is that an athlete’s own assessment of his injury is no way to judge whether he’s ready to get back in the game.

SOURCE: Neurology, October 26, 2004.