Sport is facing a crisis. For once, it is nothing to do with finances, TV rights, corruption or doping but it is possibly a much more serious issue.

It’s an issue that is likely to cut through to the very heart of sport participation: parents are growing increasingly worried that their children’s brain may be harmed by concussion, possibly irreversibly, if they are allowed to play contact sports.

It has been known for nearly 100 years, since Dr Harrison Martland’s research involving a group of boxers in 1928, that repeated concussions can lead to a form of neurodegeneration called chronic traumatic encephalopathy (CTE).

Back then, it was called punch-drunk syndrome and dementia pugilistica, with the pathognomic association being consequent to the misconception that the condition was the exclusive domain of sun-setting former boxing glories.

The discovery of the same pathological findings in many other groups exposed to repeated brain injury, such as soldiers and victims of domestic abuse, changed everything.  But real shockwaves were sent when CTE was first reported in retired American Football players some 20 years ago.

Soccer, ice hockey and other sports followed suit.  In 2012, 4,500 retired American Football players brought a legal claim against the National Football League (NFL) for “concerted effort of deception and denial in its handling of the science of concussions and brain trauma”.  A year later, without admitting any wrongdoing, the NFL settled for an initial sum of $765 million. 

Millions of dollars have since been invested in concussion research by sport authorities around world, partly out of concerns for players’ welfare, but also bowing to relentless campaigns by the media, scientists and pressure groups.

On one hand, there is great reason for alarm: one recent report found evidence of CTE in 110 of 111 brains of former NFL players. On the other hand, sceptics will point out that 110 cases is smaller a figure than the number of articles written in the New York Times about CTE in recent years and that the number is tiny considering that millions of Americans play the sport at all levels every year. 

There is no epidemiological evidence of a CTE pandemic in ageing athletes and animal work is inconclusive.  Still, many players have retired early due to concerns about their brain health and participation in many contact sports is down in almost every US state. Several American Football youth academies have shut down altogether. 

In medicine we are used to risk: all conditions and interventions require some understanding of hazards, exposure, susceptibility, probabilities and so forth. Knowing how to discuss this with patients is part of the core competencies of any doctor and medical student. Uncertainty is much more difficult to handle, particularly when cause and effect may be separated by several decades. When some experts warn that even heading the football repeatedly can lead to dementia in later life, parents take no chance.  

Most people accept a link between repeated concussion and neurodegeneration but there so much uncertainty as to the level of exposure required to cause the condition and whether individual genetic or lifestyle factors may predispose only some certain athletes to this. Some robust epidemiological studies are underway but the answer will not be quick or perhaps even conclusive. This may be not be good enough to allay the immediate concerns for players and parents but we must not lose sight of the overwhelming benefits of sport for physical and mental health and society in general - including a well-known reduction in the risk of dementia in physically active individual.  Childhood obesity is the real epidemic we should worry about, one might argue.

Meanwhile, whilst the great wheel of science inches forward, study by study, article by article, we must not forget the real and present dangers of mismanaging concussion in the acute setting. Most concussions will heal without any ill effects but, if undiagnosed, its morbidity can rapidly worsen, especially if players return to play before their recovery is complete.  

The cumulative effect of unrecovered concussions is not only a frequent cause of disabling sequelae such as intractable headaches, dizziness, fatigue, sleep disturbance, poor learning and mental health issues but, occasionally, in children and adolescents in particular, fatal brain swelling. 

To mitigate such risks, major sports authorities have issued guidance on concussion management for all levels of participation, which must be heeded. The difficulty is often diagnosing concussion in the first place, as only one in 10 concussions involve loss of consciousness and the majority of these injuries go unnoticed.

Current diagnostic tools are subjective and largely inadequate, even in professional hands.  Objective assessments are being developed, including biomarker tests emerging from ground-breaking research at the University of Birmingham. Science may come to the rescue of us worried parents before we reach for the bubble wrap after all.