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Lasting effect of concussion

Wednesday 28 January 2009

Young people who get concussion can “show subtle signs of mental and physical problems” even 30 years later, reports BBC online. The website highlights research on former athletes who had brain injuries in their youth, which found they performed worse than their uninjured counterparts at memory and coordination tests. These minor changes did not affect everyday life and all the athletes remained healthy.

This was a small study on 40 former athletes who had played the contact sports, ice hockey or American football, while at university. The athletes completed questionnaires detailing any history of concussion (brain injury) and participated in a number of psychological and coordination tests. On average the 19 athletes who reported being concussed were slightly worse at certain memory tests and were slower at a coordination test requiring them to rotate objects.

This is an interesting study but it has some limitations. The study did not measure any differences between the athletes before concussion occurred. This means it is possible, for example, that sportsmen who are generally less coordinated might be more prone to concussion and poorer performance at physical tests.

Larger prospective studies will be needed to test the extent of any possible long-term effects from concussion, and how these might affect athletes’ lives.

Where did the story come from?

This research was conducted by Dr Louis De Beaumont and colleagues from the Centre of research in neuropsychology and cognition, and other institutions in Canada.

The study was funded by the Natural Sciences and Engineering Research Council of Canada, the Canada Research Chairs programme and the Canadian Institutes of Health Research. It was published in the peer-reviewed medical journal Brain.

What kind of scientific study was this?

This was a cross sectional study investigating the link between concussion in sports, and performance in neuropsychological tests conducted 30 years after the concussion occurred.

Previous research has shown that the effects of sport-related concussion can persist for a few years after an injury, but no research had examined these effects 30 years later.

The researchers recruited 56 volunteers from the lists held by several university athletics organisations. Their ages ranged from 50 to 65 years. In total 50 volunteers had played for a Canadian university ice hockey team and six had played for American football teams.

To be eligible for the study volunteers had to have no history of alcohol or drug abuse, no major medical or psychiatric illness, no concussion reported since their time with the university team, and still be physically active (exercising at least three times a week). Of those volunteers, 10 out of the original 56 did not meet these criteria, and a further six could not recollect the concussion event in sufficient detail.

A standard questionnaire was used to obtain details about the volunteers’ number of previous concussions, their approximate date and some measures of severity such as the degree of memory loss and duration of loss of consciousness.

The research identified 19 of the volunteers as having a history of concussion; their concussion ranged in severity from episodes of confusion without loss of consciousness to prolonged loss of consciousness for several minutes. The average age of this group was 61 years. The remaining 21 previous volunteers with no history of concussion were allocated to the control group, which had an average age of 59 years. Both groups had achieved 18 years of education, on average.

Both groups were tested using a range of psychological and cognitive tests such as the Mini Mental State Examination (MMSE), an 11-question measure that tests orientation, attention, immediate and short-term recall, language and the ability to follow simple verbal and written commands.

Reaction times were tested by asking the recruits to press a button on hearing a noise. The recruits wore electrodes on their head to measure the time difference between the noise reaching the brain and the muscle activity used to press the button.

Muscle tests examined coordination using tests where participants were instructed to rotate hand-held spheres when sitting in a chair. The movement of these spheres was tracked using a computerised motion tracking system.

The results for all the tests are reported as the difference between mean values, which were then tested for statistical significance.

What were the results of the study?

The researchers say that the results in the MMSE testing was the same for both groups. The former athletes with concussion performed worse on a memory test of recognition. The groups did not differ on reaction time in the noise test.

In all four of the coordination tests using the rotating spheres (hands separately or together) the former athletes with concussion were slower by about 150 degrees per second. The researchers say that the difference was not related to the severity or number of concussions.

What interpretations did the researchers draw from these results?

The researchers say that in their study, former athletes who sustained their last sports concussion 30 to 20 years ago show cognitive and motor system alterations compared to the former athletes who had no prior history of sports concussion. They say these findings resemble those found in previous studies of athletes three years after their concussion occurred.

They also state that their study needs to be repeated with a broader range of concussion severity and injury before concussion can be considered a risk factor for deterioration of brain function.

What does the NHS Knowledge Service make of this study?

This was a small cross sectional study in which a selective sampling method has been used to divide former athletes into those who were concussed 20 to 30 years prior to the study and those who did not report a history of concussion. The authors note that:

  • There are disadvantages in relying on retrospective self-reports of concussion. The chance of recall bias is particularly strong when both groups are not blinded (i.e. they were all aware of the purpose of the study).
  • The stringent set of exclusion criteria used restricted participation to only those former athletes who remained healthy and physically active to age 65 years. This means that it is not clear if these results could be applied more generally to all athletes who have been concussed.
  • None of the concussed group reported less severe ‘grade 1 concussion’, and so this study does not apply to all concussed athletes, particularly those with “mild” concussion.
  • This study design cannot test differences in cognitive or motor skills prior to concussion. Differences at this time could account for both risk of concussion during competitive sport and the differences in these skills measured later in life.  These types of baseline differences could only be measured in a prospective study (one conducted over time).

This interesting study adds to the weight of research on sports concussion, all of which is serious and rarely considered mild.  Other studies, that compare the baseline skills of athletes and monitor the effects of concussion over time, will be needed.

It’s not possible to say for sure if sports concussion during youth can still affect performance at older ages. Questions still remain on how severe concussion needs to be to lead to long-term damage, and how much any damage might affect performance.

Analysis by Bazian
Edited by NHS Website

Links to the headlines

Sports stars suffer effects of concussion years later.

The Daily Telegraph, 28 January 2009

Concussion effect 'spans decades'.

BBC online, 28 January 2009