The impact of brain injury in sport

The effects a concussion has on the brain can last up to a year ^[1] or more with changes in white matter, brain connections and blood flow. However, the return-to-play initiatives in most sports are often no more than 21 days. When players sustain repetitive brain injuries, they are increasing their risk of early-onset neurodegenerative disease. More than 80% of concussions are diagnosed the next day, or several days later, at which point players have already been in play or training with a brain injury.

Female sports players are at least three times more seriously impacted by concussion than males, have longer recovery time, and post-concussive symptoms are more pronounced ^[2]. This is because of differences in the microstructure of the brain, the influence of hormones, coaching regimes, and the management of injuries.

Brain development peaks between ages 8-12, but the brain is still developing until early 20s. Brain injury in this crucial development phase is serious; research suggests a link between early-life concussion and the risk of mental health disorders and dementia in later adulthood ^[3]. 30% of children will experience persistent post-concussion symptoms including physical, emotional, cognitive and sleep issues ^[4]. Young athletes can exhibit cellular changes in the brain associated with CTE, even in the absence of diagnosed concussions ^[5].

Concussion can cause reduced cognitive function, changes in reaction time, impairments in balance, and neuromotor responses leading to awkward movements during jumping and landing ^[6]. A significant association exists between a history of concussion and lower extremity injury ^[7], especially an increased odds of ACL injury ^[8], lateral ankle sprain, knee injuries and muscle strains. Athletes at all levels in sport have a greater risk of lower-body injury issues for more than a year following a sport-related concussion. In some cases, this risk is as high as 67%.

In professional sport, there is a clear relationship between days out due to injuries and the difference between a team’s final position against their expected position ^[9]. Competitive teams must adapt their tactics or style in order to fill the hole left by injured players. For players, injuries mean that they also risk losing their place in the team. Even with just weeks out from playing, a new manager could come into a club and a new play style deployed.

In the past 20 years, there has been a greater interest in the long-term consequences of brain injury in contact sport. Understanding and appreciation of brain trauma have also shifted from singular traumatic brain injury and concussion, to the cumulative exposure of repetitive sub-concussions over the course of a playing career.

What began with research into the effects of impacts to the head for American football (NFL) players has now opened a global discussion on the long-term consequences of brain injury in sports.

Repetitive head injuries and neuroinflammation are strongly associated with neurological disorders including Alzheimer’s disease ^[10], Parkinsonism  ^[11], anxiety, depression, post-traumatic stress disorder (PTSD), Amyotrophic Lateral Sclerosis (ALS) ^[12] and Motor Neurone Disease (MND) ^[13]. The medical and sporting worlds now recognise the increasing number of contact sports players developing Chronic Traumatic Encephalopathy (CTE).

CTE is a progressive neurodegenerative disease that leads to early-onset dementia. Symptoms include:

• Memory problems;
• A decline in thinking ability;
• Confusion;
• Aggression;
• Depression; and
• Changes in personality.

It is debilitating and life-changing for those affected and their families and friends.

Typically, CTE occurs in players in their 30s-50s, but can occur in teenagers ^[14]. Initially, symptoms are of mild forgetfulness, low mood, quick escalation to anger, and slowing of thought process, which then gradually progress to loss of independence and dementia.

The risk and severity of CTE is caused primarily by the cumulative damage of multiple sub-concussive impacts, and not by one-hit concussions ^[15]. Sub-concussive impacts are those which are of sufficient force to adversely affect the function of brain cells but do not cause symptoms of concussion. Players and those around them are not aware of these impacts.

20% of people with CTE diagnosed after life were recorded as never having sustained a single concussion.

The perception that only boxing, American football, rugby and AFL (Australian rules football) create brain injury risk is both unfair and untrue. This perception has been largely fuelled due to the focus on concussion, where a head impact (head-to-head, to ground, knee, ball etc) causes an acute brain injury with symptoms e.g. headache, nausea, balance and co-ordination. While these sports contribute to players having concussions and sub-concussions every season, so does football (soccer), hockey, curling and combat sports.