Brain injury blood test to help concussion sufferers return to play

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© Mike Bain

A new blood test for assessing brain injury is being studied in Sweden, adding an objective test to evaluations of whether a concussed sports person is fit to return to play.

In other new research relating to concussion, US scientists have found that women have a longer recovery period than men, but the symptoms of women who take a hormonal contraceptive are lessened compared to those who do not.

And a 36-year-long study has found that sustaining a traumatic brain injury (TBI) is associated with an increased risk of developing both dementia and Alzheimer’s disease.

Blood test identifies brain injury biomarkers 

In a Swedish study of concussed hockey players, researchers at Sahlgrenska Academy identified a superior blood-based biomarker for assessing subtle brain injury.

Dr Pashtun Shahim
Dr Pashtun Shahim

In a study published by the journal Neurology, researchers compared concentrations in the blood of known biomarkers for concussion, both directly after the event and over a period of time. The results show that it was the levels of the protein neurofilament light (NfL) that had the clearest connection to the severity of concussion, measured as the number of days it took for players to return to play.

Blood samples were taken from 87 who sustained a concussion one, 12, 36 and 144 hours (six days) after the concussion. A fifth sample was taken at the time when the person was determined fit to return to unrestricted competition.

“The strength of this study is that we longitudinally followed how these biomarkers are released and cleared from the blood. What we observed was that NfL was released within an hour after the concussion, and then it increased over time in players who had prolonged symptoms,” said lead author Dr Pashtun Shahim.

The levels of the other biomarkers that were studied (tau, S100B and neuron-specific enolase, NSE) decreased quickly and could thereby not indicate how injured the players were after 7-10 days, a time point many players returned to play in the study.

“It is important to protect the players from developing long-term symptoms by avoiding premature return to play. Suffering additional concussion, especially when the current post-concussion symptoms are not fully resolved might have long-term consequences,” Shahim said.

Dementia risk increased after TBI
One of the largest studies of its kind finds that risk of dementia increases with the number and severity of injuries.

A study by Danish and American researchers and published in The Lancet of 2. 8 million people over 36 years found that people sustaining a Traumatic Brain Injury (TBI) were 24% more likely to be diagnosed with dementia than those without a history of TBI over the study period.

Dr Jesse Fann
Dr Jesse Fann

The risk of dementia increased with the number of TBIs and severity of injury, and even a single mild TBI (concussion) was linked with a higher risk of dementia. The study is one of the first to have a sufficient sample size and follow-up time to assess the effect of TBI in younger adults on long-term dementia risk.

“Individuals with a history of traumatic brain injury, including those with less severe injuries have an increased risk of developing dementia, even decades after the injury”, says Jesse Fann, Professor of psychiatry and behavioural sciences at the University of Washington School of Medicine, in Seattle, USA, who led the study.

“However, it’s important to emphasise that although the relative risk of dementia is increased after traumatic brain injury, the absolute risk increase is low. Our findings do not suggest that everyone who suffers a traumatic brain injury will go on to develop dementia in later life.”

Dementia affects 47 million people worldwide, a number expected to double in the next 20 years. Every year, more than 50 million people worldwide experience a TBI.

The researchers found that a single severe TBI increased the risk of dementia by 35% (0.8% of participants with dementia had at least one severe TBI vs 0.1% of participants without dementia), whilst one mild TBI increased the risk by 17% (4.3% vs 4.0%).

Importantly, the younger the individual sustaining a TBI the higher the risk of subsequent dementia, when taking time since TBI into account. For example, individuals having a TBI in their 20s were 63% more likely to develop dementia about 30 years later compared to those who didn’t sustain a TBI in their 20s; whereas individuals sustaining a TBI in their 30s were 37% more likely to develop dementia 30 years later compared with those without a TBI in their 30s. The findings also show that men with a history of TBI had a slightly higher risk of developing dementia than women.

“Significant differences” between men and women who suffer concussions

A study comparing male and female athletes found there were significant differences between male and female college varsity athletes in post-concussion symptom severity and length of recovery. In addition , differences among the women depending on hormonal contraceptive use were reported in the study, published in Journal of Neurotrauma.

Researchers measured peak symptom severity following concussion among the study participants and length of time to recovery, defined as the period of time between the injury and when they were cleared to return to full play. Within the group of female study participants, the researchers compared outcomes among hormonal contraceptive users and non-users.

Previous studies examining sex differences in outcomes following concussion yield conflicting evidence. Some studies report that females experience greater symptom burden and greater cognitive deficits in certain domains than males post-concussion. Other studies, however, do not find any significant sex differences in symptoms or cognitive performance post-concussion. Ambiguity regarding sex differences in post-concussion symptom levels may stem, in part, from a reporting bias, as females may be more likely than males to be forthcoming when reporting concussion symptoms.

Preliminary evidence suggests that hormonal contraception (HC) may moderate outcomes in female athletes following concussion. In the single human study to date examining this topic, concussed women taking oral contraceptive pills (OCP) had significantly lower total symptom severity and fewer number of symptoms than concussed women not using OCP. In the rodent model, higher estrogen levels exacerbated brain injury effects in female rats. OCP regulate, and generally lower, estrogen and other female reproductive hormone levels in the body. Therefore, the decrease in circulating hormone levels found in HC users may be a protective factor following concussive injuries.

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