Experiencing multiple concussions may be linked to worse brain function in later life, suggests a study of nearly 16,000 people.
Among 15,764 people aged 50 to 90, those who reported three or more concussions had worse complex planning and attention scores on a range of cognitive tests.
People who had experienced four or more concussions showed poorer attention, processing speed and working memory.
“What we found was that … you only really need to have three lifetime concussions to have some kind of cognitive deficits in the long term,” said Dr Matthew Lennon, the study’s lead author and a PhD candidate at the University of New South Wales’s Centre for Healthy Brain Ageing.
“If you have multiple concussions in your teens, 20s, 30s and 40s, you will still be feeling the effects when you’re 70 or 80.”
The findings come the day after the first hearings of a Senate inquiry into concussions and repeated head trauma in contact sports. The inquiry was established in the wake of increasing public concern and ongoing reporting by Guardian Australia about sporting organisations’ management of player concussions and the effects of long-term exposure to heavy knocks that may not result in a clinical diagnosis of concussion but still cause damage to the brain.
A large and growing body of scientific evidence has shown links between repeated exposure to head injury and sub-concussive blows in contact sports and the neurodegenerative disease chronic traumatic encephalopathy (CTE), which has been found in the brains of multiple Australian sportspeople, from amateurs to professionals.
Lennon’s research found that while people who had experienced repeated concussions had measurably worse cognitive performance, the differences were not drastic. “We’re not talking 20 or 30 IQ points – we’re talking maybe a couple of IQ points’ difference,” Lennon, who is also a medical doctor, said.
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The benefits of sport to physical and cognitive health were significant, Lennon emphasised. “When we looked at the subgroup analysis [in data yet to be published] … if you’d suffered a concussion while playing sport, you actually had better working memory and processing speed than those who had never suffered a concussion at all.
“What that tells us is that even if you have been concussed the benefits of playing sport, particularly as a young person, outweigh the risks to your long-term cognition,” Lennon said. “That makes sense when we look at the overall data because we know that blood pressure, high cholesterol, diabetes … they’re all really significant risks to our cognitive health.”
Lennon’s research did not investigate CTE or the cumulative effect of exposure to sub-concussive blows.
The paper argued, however, that given the “hotly debated” issue of when people ought to stop participating in higher-risk activities, such as contact sports, the finding that three or more concussions caused long-term cognitive deficit offered a benchmark.
“This is a critically important result. It gives a clear threshold at which mid to late life cognitive deficits can be realistically expected,” the paper said. “When making recommendations for those who have suffered recurrent [traumatic brain injury] clinicians should be cognizant that some long-term cognitive deficits can be expected after 3 or more.”
The research, published in the Journal of Neurotrauma, forms part of a wider project known as the Protect study, which follows UK participants for up to 25 years to understand factors affecting brain health in later life.
Lennon said a benefit of his study was its non-athlete cohort, as most previous studies into the link between concussion and cognitive outcomes had focused on professional or university athletes. “They haven’t really included the average person.”
On average, participants reported their last head injury 30 years prior to the study. The study’s authors conceded the long period that had elapsed since the experiences of concussion was a potential limitation.
“The retrospective design of the study, with elderly participants often recalling details of events more than three decades in the past, may have caused an underreporting of head injuries and thus an underestimate of the size of their effect,” they wrote.