Three or more concussions may be linked to worse brain function in later life, according to a new study of nearly 16,000 people.

Multiple concussions in a lifetime were shown to affect the ability to plan and pay attention. People who had experienced four or more concussions showed poorer attention, processing speed, and working memory.

The UK-based research, conducted by UNSW Sydney, the University of Oxford, and the University of Exeter, involved 15,764 participants, aged 50 to 90 years of age, in the largest study to explore the effects of concussion or traumatic brain injury to date.

Senior study author from the University of Oxford, Dr Vanessa Raymont said people with a history of concussions should be wary of the potential dangers of continuing activities placing them at risk of further head trauma, like contact sports and dangerous work.

Dr Raymont also said organisations operating in areas where head impact is more likely should be encouraged to consider how they can better protect their athletes or employees.

“We know that head injuries are a major risk factor for dementia, and this large-scale study gives the greatest detail to date on a stark finding – the more times you injure your brain in life, the worse your brain function could be as you age,” Dr Raymont says.

Unlike previous studies into traumatic brain injuries (TBI) that mostly looked at athletes and younger people, examining cognitive outcomes over weeks to months and sometimes up to years, the online PROTECT study, launched in 2015, looks at the general population and cognition on average 20 to 30 years after their last head injury.

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 said despite the robust findings of the study and the validation of the findings when compared to other epidemiological studies, there were some limitations.

“The retrospective design of the study, with elderly participants often recalling details of events over three decades in the past, may have affected the reporting of head injuries, even while using a well-validated screening tool,” Dr Lennon says. 

“Memory gets fuzzy especially as you get more distant from the event, being precise about what exactly happened is going to be challenging and that does put a bit of grey on the results.”

The researchers also acknowledge that some unmeasured covariates known to affect cognitive scores may have also influenced the study results.

“We were able to control for the critical confounding variables including age, sex, education, smoking and vascular risk, but unmeasured confounders such as socioeconomic status may explain some of the variation between groups,” Dr Lennon says.

Dr Lennon says he hopes the findings will be incorporated into recommendations looking at how to best prevent and counsel people who have been concussed, or are at high risk of further concussion, beyond focusing on professional and university athletes.

Lead Author Dr Matthew Lennon