When 49ers inside linebacker Chris Borland announced his early retirement from the NFL after just one season, the league and fans reacted with shock. But as a father, a neuroscientist and a geriatrician, I can imagine all too well the immense relief that Borland's parents likely felt knowing they would no longer have to watch their son take a beating on Sunday afternoons.
My life's work is ending Alzheimer's disease and related dementias, the very things that Borland feared developing in his later life. I am deeply committed to strengthening our scientific understanding of the causes of dementia--including untangling the impact of sports-related childhood concussions (the sort that Borland suffered before entering the NFL) on later-life cognitive function.
As a parent, it wouldn't take much evidence for me to decide to keep my two now grown children out of high-impact sports like football and soccer. But as a scientist and a physician, I have a different perspective: I can see clearly just how much we still don't know--and how much we need to learn--to make well-founded, smart public health recommendations about childhood sports participation and concussion risks.
When it comes to adult traumatic brain injury and dementia risks, the evidence is more established. Last year, the NFL stated in federal court documents that it expects nearly a third of its retired players to develop long-term cognitive problems and predicted that the conditions are likely to emerge at "notably younger ages" than in the general population.
There's a key difference, though, between what we know about the link between adult traumatic brain injury and later life dementia, and what we know about childhood concussions and later life dementia. The truth is, we know very little about how childhood concussions influence the risk for dementia in adulthood. We need to accelerate this research so that parents and coaches can make better decisions about youth sport participation, practice policies and competition rules.
This month, I co-authored a consensus statement published in Nature Reviews Neurology about the need to advance research into the short-term and long-term neuropsychological outcomes of youth sports-related concussions. The statement was the result of a meeting convened by Safe Kids Worldwide, the Alzheimer's Drug Discovery Foundation and the Andrews Institute for Orthopaedics and Sports Medicine. The meeting brought together more than 25 experts in a variety of fields including neurology, sports injury reporting, ethics, genetics, biomarkers, dementia and neuroimaging. The group concluded that there is not enough evidence to establish a clear link between early-life repetitive head impacts and adult cognitive decline and dementia. This is contrasted by what is known about similar head impact injuries in adults and the established risk of later-life cognitive decline and dementia.
So how can we get answers about childhood concussions and late life dementia risks? We need to improve our understanding of the fundamental biology of concussions and how factors like age, sex and genetics influence concussion susceptibility and recovery. We need to support continued research and development of brain imaging techniques that shed light on the pathology of pediatric brain injury and have the potential to accelerate the development of novel therapies.
Moreover, we need to improve local and nationwide injury surveillance, eventually tracking youth athletes from the beginning of their athletic careers. According to the CDC, there were 250,000 nonfatal traumatic brain injuries recorded among individuals under the age of 19 in 2009, constituting 65 percent of all sports-related concussions. Many more may have incurred undiagnosed concussions and could suffer consequences in the future.
With better monitoring we can improve our understanding of the scope of the problem by conducting a large, long-term study following youth athletes across their athletic careers to determine the influence of repetitive head impacts on the risk of developing late-life cognitive decline and dementia.
The bottom line: we need to establish and encourage clear lines of research in many different but complementary fields to improve our knowledge and translate that data into actionable guidelines.
Chris Borland did not make his decision lightly, but he had the benefit of stronger research surrounding the link between adult concussions and dementia risk.
"The decision was simple after I had done a lot of research and it was personal," Borland said on "Face the Natioon" on Sunday, March 25. "I was concerned about neurological diseases down the road if I continued to play football.
It's not yet a simple decision for the parents of children playing high-impact sports. But with more research and better surveillance, we can ensure that parents, coaches, policymakers and physicians have the information they need to make educated decisions to protect the long-term health of young athletes.