Professional football players who started tackle football before age 12 years had a greater cognitive impairment in later life than their contemporaries who started playing later than age 12, according to a new study.
"Our results suggest that exposure to repeated head impacts at a critical time of brain development in childhood is associated with later life cognitive difficulties," senior author Robert A. Stern, PhD, Boston University School of Medicine, Massachusetts, commented to Medscape Medical News.
He stressed that "We can't make policy recommendations on our findings as this is just one study and it was performed in former professional football players, a highly select group. We need more studies of individuals who have played football at different ages — those who only played at youth level or high school or at college to really understand this association in a more generalized population.
"But having said that, there is growing research evidence that even one season of playing tackle football can have a negative effect on brain structure and function," he added.
Dr Stern urged more careful thought about head impacts in children under 12. "Just because we don't have adequate data for definitive answers doesn't mean we shouldn't use logic. We need to err on side of caution."
Their study was published online in Neurology on January 28.
"Err on the Side of Caution"
Dr Stern noted a robust area of research showing that in boys a key period of brain development occurs around ages 10 to 12 years. "At this time several brain structures reach a peak of development. These include cortical thickening, increase in the volume of the hippocampus and amygdala, and increase in myelination in the white matter. We believe that if the brain is injured at that critical time, it could lead to long-term consequences."
"In this society we do everything possible to protect our children from illness and harm, but we drop them off at football every week and encourage them to regularly hit their heads. That doesn't make much sense to me."
For the current research, Dr Stern and colleagues studied a sample of former NFL American football players who were already taking part in another study of former footballers with cognitive issues.
From this group, they selected 21 age-matched pairs (with current ages of 40 to 69). In each pair 1 participant was under 12 and 1 was over 12 when he started playing tackle football.
All participants underwent three cognitive tests: the Wisconsin Card Sort Test, Neuropsychological Assessment Battery List Learning test, and Wide Range Achievement Test, 4th edition.
Results showed that even after adjustment for the total number of years playing tackle football, those who started playing when younger than 12 years of age did significantly worse in all the tests, indicating executive dysfunction, memory impairment, and lower estimated verbal IQ.
In an accompanying editorial, Christopher M. Filley, MD, University of Colorado School of Medicine, Aurora, and Charles Bernick, Lou Ruvo Center for Brain Health, Cleveland Clinic, Ohio, point out that the study has several limitations, including the possibility that it may be cumulative exposure to head impacts — which cannot be measured in a retrospective study — rather than age of exposure that is responsible for the reported results.
They reiterate Dr Stern's caveat that the study group of retired professional athletes, all of whom had some cognitive or behavioral symptoms, makes it difficult to generalize the results to society at large.
Despite these shortcomings, the editorialists say these data add to the concern about the safety of football in children. The data need substantiating, but "contact sports such as football may require careful consideration in children, who may appear to be resilient to mTBI [mild traumatic brain injury] but could be at risk for cognitive dysfunction decades later."
Dr Stern noted: "At present there are arbitrary ages set at which children are allowed to start tackle football. But we need real data to guide us in these decisions, and our study is the start of this process."
He said that while bigger blows that cause symptomatic concussion are now taken seriously, the smaller impacts that don't cause symptoms are largely ignored. "But our results suggest they could have a major role in the development of longer-term problems for the brain."
300 Head Impacts in Just One Season
He reported that one study has shown that children aged 9 to 12 years sustain an average of 300 head impacts in just one football season.
"This number will be higher in older players. And while helmets do a good job at reducing the risk of skull fractures, they don't protect the brain from the sudden movement that occurs when the head is hit. This can cause the brain to shift inside the skull, which can lead to axons sheering, causing cell destruction. We need to think about the logic behind these observations.
"I am not advocating that children do not engage in team sports," he added. "These provide important benefits for health and fitness, confidence and social skills. But they can play team sports without hitting their heads."
The study was supported by grants from the National Institutes of Health (NIH), and participant travel was funded by JetBlue Airlines, the National Football League (NFL), and the NFL Players Association. Dr Stern receives grants from the NIH, and research support from Sports Legacy Institute, the Alzheimer's Association, the National Operating Committee on Standards for Athletic Equipment, Avid Radiopharmaceuticals, Eli Lilly, Eisai Pharmaceuticals, Janssen Alzheimer's Immunotherapy, Pfizer, and Medivation. He is a paid consultant to Athena Diagnostics and serves as an expert advisor to attorneys for cases pertaining to the long-term consequences of repetitive brain trauma. He receives royalties from Psychological Assessment Resources for the publication of neuropsychological tests. Dr Bernick receives funding for the Professional Fighters Brain Health Study from Top Rank Promotions, Zuffa, Golden Boy Promotions, and Bellator. Dr Filley has disclosed no relevant financial relationships.
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Cite this: Starting Tackle Football Young Linked to Later Cognitive Issues - Medscape - Feb 05, 2015.