High School Football: No Link to Later Cognitive Decline

Pauline Anderson

July 05, 2017

Playing high school football is not associated with cognitive impairment later in life and, in fact, may help prevent depression and lead to greater lifetime levels of physical activity, new research suggests.

The potential link between repeated head injuries in sports and cognitive issues, such as chronic traumatic encephalitis (CTE), has received a great deal of research attention lately, but most studies to date have looked at professional football players.

"Important as that is, there are many more people who play high school football," study author Dylan S. Small, PhD, Department of Statistics, The Wharton School, University of Pennsylvania, Philadelphia, told Medscape Medical News.

The new analysis, published online July 3 in JAMA Neurology, included men graduating from Wisconsin high schools in 1957 who were followed up in the Wisconsin Longitudinal Study.

Of the 3904 men eligible for the study, almost a third did not have primary outcome data. Among the remaining 2692 grads, 31.0% played high school football.

The study included a matched control group of participants who did not play high school football (all controls), a subset of those who did not play any high school sports (nonsport controls), and another subset who played a noncollision sport, such as basketball or baseball, but not football (noncollision sport controls).

There were four comparisons:

  • Football vs all controls;

  • Football vs noncollision sport controls;

  • Football vs nonsport controls; and

  • Noncollision sport vs nonsport controls.

A primary analysis included cognitive impairment at age 65 years, assessed by using a composite measure from the Letter Fluency and Delayed Word Recall tests. Research suggests that these tests are the most pertinent to traumatic brain injury.

Another primary endpoint was depression at age 65 years, assessed with a modified Center for Epidemiological Studies' Depression (CES-D) scale.

Secondary analyses included the composite cognitive score at age 72 years; depression scores at ages 54 and 72 years; individual cognitive test scores; and measures of anger, anxiety, hostility, alcohol intake, and regular physical activity.

For the combined cognitive score, cutoffs, per standard deviation criteria, were 0.16 for small effects, 0.41 for medium effects, and 0.65 for larger effects. For the modified CES-D score, cutoffs were 2.56 for small effects, 6.41 for medium effects, and 10.25 for large effects.

Researchers reported 97.5% confidence intervals (CIs). Because the study included two primary outcomes, researchers wanted to have "a more stringent criterion" for reducing error, said Dr Small.

No Difference in Cognition

The study showed football players did not have significantly different composite cognition scores than all controls (–0.04; 97.5% confidence interval [CI], –0.14 to 0.05; P = .37), and the 97.5% CI contained only effects smaller than the small-effect cutoff (0.15).

Although composite cognitive scores for football players were not significantly different from those in each control group, the authors note that compared with nonsport controls, the 97.5% CI contained some effects above the small-size cutoff, but none above the medium-size cutoff (0.41).

Noncollision sport controls and nonsport controls were not significantly different.

For depression, modified CES-D scores of football players were significantly lower (–1.75; 97.5% CI, –3.24 to –0.26; P = .01) than those of all controls, meaning that they reported fewer depressive symptoms.

The 97.5% CI suggested that playing high school football could have a beneficial effect above the small-size cutoff (2.56) but not above the medium-size cutoff (6.4).

For secondary outcomes, the analysis showed that cognitive impairment at age 72 years was similar to that at age 65 years. Compared with all controls, football players had lower modified CES-D scores at age 54 years and 72 years of age, but the differences were not statistically significant.

Apart from the Immediate Word Recall test, none of the 97.5% CIs for individual cognitive tests contained values larger than the small-effect cutoff. In football players, anger, anxiety, and hostility indices at all ages did not significantly differ from those of controls.

Football players were no more likely than controls to consume a large amount of alcohol at various time points

In addition, compared with all controls and nonsport controls, football players were significantly more likely to engage in regular moderate to vigorous physical activity at age 35 years. They were not significantly more or less likely to engage in such activity than were noncollision sport controls.

Limitations

It's difficult to conclude from the results that playing football actually causes players to be more physically active at a later time point, said Dr Small. "Presumably, people playing sports are already inclined to be more physically active from an athletic standpoint."

An analysis of graduates with available genotype data found that the presence of an additional APOE ε4 variant did not significantly modify the association of playing high school football with composite cognitive scores or modified CES-D scores at age 65 years.

The authors note that because 31% of eligible participants were missing both primary outcomes, the results may be limited by selection bias.

There is no information on how many of the graduates continued to play football after high school, which is "unfortunate," said Dr Small. He also acknowledged that the researchers didn't have information on what position on the field the athlete played.

"Not having player position information is a considerable limitation because maybe there is a subgroup, for example, of people playing offensive or defensive line positions, who may be at higher risk."

The study also did not have information on concussions. Again, perhaps there's a subgroup of players with concussions whose risk for later cognitive problems was greater, said Dr Small.

A central question about playing football is what is the safe "dose" — or how often you have to play the game before it starts to put you at higher cognitive risk — he added.

"Our study is saying that the dose of playing football as it was played in high school in the 1950s doesn't seem to carry a big risk."

However, the game today is much different. For example, the rules have changed, as have training techniques, protective equipment, and awareness about safety.

"Although high school football today may be safer as a result of these changes, it is possible that the frequency and severity of head impacts have increased owing to the faster pace of the game, the larger body size of the players or an increased perception of safety," the investigators write.

Results "Far From Conclusive"

Commenting on the findings for Medscape Medical News, Frank Conidi, MD, director, Florida Center for Headache and Sports Neurology, team neurologist for the Florida Panthers hockey team, and president of the Florida Society of Neurology, noted that the equipment used today is "pretty similar" to that used in the 1950s.

However, said Dr Conidi, current players in some positions are slightly larger and are generally faster and more athletic.

Dr Conidi is studying cognitive outcomes, including dementia, in former professional football players, who likely started to play the game in high school, if not before.

Although Dr Small is hesitant to extrapolate the findings to the football scene of today, he said they may be "a comfort" to people who played high school football decades ago and are concerned about CTE.

In an accompanying editorial, Allison R. Kaup, PhD, and Kristine Yaffe, MD, both from the San Francisco Veterans Affairs Healthcare System and the University of California, San Francisco, also suggest the study results provide "some reassurance" that CTE is not "a widespread epidemic" among former high school football players.

However, the editorial writers pointed out some limitations that make the study results "far from conclusive in understanding the potential long-term risks of playing football."

Most important of these limitations was the lack of information on concussion history, they note.  

"The study evaluates the overall effect on long-term outcomes of playing football vs not playing football, but it does not directly evaluate the association of football-related exposure to concussion or sub-concussive injury with outcomes in older adulthood," they write.

In addition to not tracking the number of concussions or looking at field position, the researchers didn't consider when study participants started to play football, said Dr Conidi.

He stressed that duration is an important factor. "We see that in our research: The longer you play, as well as what position you play, makes a difference. Getting constant, even smaller, hits is what we're seeing when we talk about individuals going on to develop dementia."

Dr Conidi's research suggests that offensive and defensive linemen tend to have more cognitive problems later.

Another study limitation was that the cognitive testing used "is quite lacking," said Dr Conidi. He uses a cognitive battery that is "significantly more detailed" when testing former professional football players.

Despite these limitations, Dr Conidi was impressed by the study overall.

"The sheer numbers of individuals they looked at and the longitudinal nature of it was very impressive," he said. "There has never been anything close to this, and that, from a scientific standpoint, is amazing."

The study authors have disclosed no relevant financial relationships. Dr Kaup reported receiving access to cognitive software and tablet devices by Akili Interactive Labs for use in a research study related to traumatic brain injury and cognition in aging. Dr Yaffe reported serving on drug safety monitoring boards for Takeda Inc and a National Institutes of Health–sponsored study and serving as a member of the Alzheimer's Association Medical and Scientific Advisory Council and as a Senate member of the Council of the German Center for Neurodegenerative Diseases.

JAMA Neurol. Published online July 3, 2017. Abstract, Editorial

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