In the know

Females are at least three times more seriously impacted by brain trauma than males, with recovery time longer and post-concussive symptoms more pronounced ^[2].

This is due to:

• Differences in the microstructure of the brain ^[3], female axons particularly in the white matter tend to be smaller with fewer microtubules, and more likely to be damaged than those of males at the same force application level;
• Hormones and the influence of progesterone on the outcome. In the menstrual cycle there is a significant fluctuation of progesterone levels, whereas males have lower background levels of progesterone;
• Significant differences in head and neck geometry and neck strength in males versus females. Females have a total neck muscle mass to head weight ratio of 1 to 9.36 as compared to a 1 to 3.11 ratio in males; and
• Coaching regimes and the management of injuries.

Consequently, women tend to experience concussion injuries at a lower average impact threshold ^[4].

Research found that women who were injured during the last two weeks of the menstrual cycle (when progesterone was at its highest) had worse post-concussion symptoms compared with women injured during the first two weeks – when progesterone was low ^[5]. As hormones fluctuate, grey and white matter volumes change, as does the volume of cerebrospinal fluid. Progesterone is associated with increased tissue and decreased cerebrospinal fluid volume ^[6].

Females show diminished performance on visual memory and total combined memory function scores after sports-related concussions ^[7].

Females typically experience intercurrent depression at a rate twice that of males, and tend to experience a more widespread and diverse pattern of post-concussional symptoms ^[8].

Certain post-concussion symptoms also appear to be more prevalent in women, particularly those of headache, dizziness, fatigue, irritability, and concentration problems three months after sustaining a concussion ^[9].

It has been 20 years since sex and gender differences were first seen in brain injury research, yet 80.1% of all concussion research data comes from males ^[10]. This lack of female data means the true extent of damage is likely to be underestimated. Most women, their coaches and medical support are still unaware.

Between ages 8-12 is when peak development of the brain occurs, but the brain is still developing through the refinement and rearrangement of pathways and connections between cells until early 20s.

• Players experiencing head impacts prior to age 12 have been found to have demonstrated worse cognitive, executive (planning, decision-making, impulse control) and new learning abilities as adults, compared to those who were at least 12 years old when they were first exposed to contact and collision sports ^[11].
• Children and young people who sustain a concussion are at increased risk of developing mental health issues (anxiety and neurotic disorders, behavioural disorders, mood and eating disorders, schizophrenia, substance use disorder and suicidal ideation) ^[12].

Axons are the tail-like structures that connect neurons in the brain and connect neurons to other cell types. Axons are coated in myelin, and this improves how electrical discharges transfer information along the axon – it is crucial to healthy brain function.

This myelin is formed as the brain develops. It occurs mainly between the second trimester of gestation and the early years of postnatal life, and continues until the mid-20s. Myelin development is linked to cognitive skills in children, as when myelination improves, the brain works faster.

So, children have less myelin than adults. This is problematic, because myelin protects the axon. Axons with little myelin are more exposed and prone to damage from concussions and sub-concussions. Less myelinated axons also don’t recover as well from injury as highly-myelinated axons. This means a child is more vulnerable to brain trauma in sports. Children’s brains undergo noticeable changes after just one season of head impacts, even if they were never diagnosed with a concussion ^[13].

Research has shown that school pupils and students who experience multiple concussions often struggle with academic performance and learning behaviours long-term ^[14].

We now know more from research about how the brain responds to rotational forces, than in the past; we know a child’s/youth is more susceptible to these forces. What we don’t know is which child may have a genetic or metabolic risk factor, who will continue to play sport into adulthood and or as a professional, so given the damage of sub-concussions and rotational forces are cumulative, every child is at risk of a massive lifetime dose of sub-concussions and rotational forces. Consequently, their CTE and risk of neurodegenerative disease starts in childhood.