Heading in Soccer Linked to CNS Symptoms

Pauline Anderson

February 06, 2017

Heading a soccer ball, a mainstay of what is arguably the world's most popular game, may be more than just a minor subconcussive event, new research suggests.

A new study showed that both intentionally hitting the ball with the head, called "heading" the ball, and unintentional head injury, such as bumping another player or a goalpost, are independently associated with central nervous system (CNS) symptoms, such as pain and dizziness.

"I'm not saying that heading is a routine cause of concussion," study author Michael L. Lipton, MD, PhD, professor, Departments of Radiology and Psychiatry and Behavioral Sciences, Albert Einstein College of Medicine, New York, New York, told Medscape Medical News.

"What I am saying is that heading, or at least high amounts of heading, is by no stretch an uncommon cause of symptoms, which means we need to think about what the bigger implications are for function."

Their findings were published online February 1 in Neurology.

Common Wisdom

The common wisdom has been that accidental or unintentional collisions in soccer were the major cause of concussions. Heading was considered less of a concern because it's a "controlled, deliberate act" and if a player uses the correct technique, the impact would have less effect than colliding with another player, said Dr Lipton.

Heading was also felt to be "more benign" because the magnitude of an impact is generally less with a ball, which is more "compliant" than someone's head, he added.

However, as Dr Lipton pointed out, a soccer ball can travel at tremendous speeds — the highest detectable speed in professional soccer is about 120 miles per hour.

For this analysis, the researchers used data from a subgroup of the Einstein Soccer Study, including 222 adult participants, 79% of them male, who had played amateur soccer 6 months a year for at least 5 years.

Participants completed questionnaires (HeadCount surveys) that asked about intentional and unintentional head impacts during soccer practices and games over the previous 2 weeks. Researchers felt that this time period was short enough for players to accurately recall recent activity but long enough to capture a meaningfully amount of such activity.

Participants reported frequency of heading and severity of CNS symptoms on a scale of 0 to 4 (0 = very low impact with no pain; 1 = mild impact with slight pain; 2 = moderate impact with pain, some dizziness; 3 = severe impact, felt dazed, stopped play, needed medical attention; 4 = very severe impact where knocked unconscious).

Of the 222 participants reporting soccer activity, 58 completed 2 questionnaires and 80 completed 3 or more, for a total of 524. Researchers had data on heading from 470 surveys and on unintentional exposures from 481 surveys.

The mean number of headings was 44 for men and 27 for women. At least one unintentional head impact was reported by 37% of men and 43% of women. About 20% of respondents reported heading-related CNS symptoms.

Heading Comparison

More frequent headings (highest heading quartile) were associated with CNS symptoms (odds ratio [OR] vs lowest heading quartile, 3.17; 95% confidence interval [CI], 1.57 - 6.37) after controlling for unintentional impacts.

One unintentional impact was independently related to CNS symptoms after controlling for heading (OR, 2.98; 95% CI, 1.69 - 5.26), but two or more such impacts had a stronger association (OR, 6.09; 95% CI, 3.33 - 11.17).

"What's new here is that heading is a cause of CNS symptoms, some of which are probable concussive events," said Dr Lipton.

He pointed out that heading were happening "a fair amount" during only a 2-week window and that the association with symptoms was independent of other collisions.

The researchers looked at the effect of neck circumference, a surrogate marker for muscle mass. Another common wisdom, not supported by much evidence, is that neck strength helps stabilize the neck and is protective when it comes to concussions, said Dr Lipton.

"The idea is that if you have a long, spindly neck with poorly developed muscles, and the ball hits your head, your head is going to be knocked around more, leading to more potential for injury and symptoms."

But the researchers found that having a bigger neck had no effect on the associations. "This means that having a thicker neck, or more muscle, doesn't make you less likely to have concussive-like symptoms, as a consequence of either a collision or heading," said Dr Lipton.

In soccer, men tend to head more than women, but "we didn't find that the association with symptoms was clearly different between men and women," although the study wasn't specifically designed to find such differences, said Dr Lipton.

In female athletes, "it is highly likely that soccer is the sport with the greatest concussion risk," according to the 2013 American Academy of Neurology guidelines on the evaluation and management of concussion in sports.

Of all high school sports — among both males and females — women's soccer is second only to boys' football in terms of concussion risks, said Dr Lipton.

"Women are less likely to have a concussive event simply because they don't engage as much in activities that have that kind of risk, but they are more likely to have persistent symptoms as a result of a concussion," he explained.

There are no guidelines pertaining to heading for adult soccer players in the United States. Officials overseeing youth soccer recommend that children under age 14 years should not head the ball, at least in competition, said Dr Lipton.

A paper by Dr Lipton and his colleagues (Radiology. 2013;268:850-857) that didn't investigate symptoms but rather brain changes on MRI and cognitive functioning shed some light on whether there might be a safe amount of heading in soccer.

"We found that once people had in the range of 800 to 1000 headers over the past year, their risk of having detectable changes in their brain was significantly elevated, and for their cognitive function to be affected, it took more like 1800 over the past year."

But Dr Lipton stressed that it's not clear where exactly the threshold lies and that it likely varies between individuals.

Because the study included only adult soccer players in the northeastern United States, the results can't be generalized to adolescents and younger children or to players elsewhere.

The long-term implications of the associations between head impact and CNS symptoms aren't yet clear, said Dr Lipton.

On the Research Agenda

In an accompanying editorial, Hester Lingsma, PhD, Department of Public Health, Erasmus MC University Medical Center, Rotterdam, the Netherlands, and Andrew Maas, MD, PhD, Department of Neurology, University of Antwerp, Belgium, highlighted some of the study's several strengths.

One is that while previous research generally calculated the combined effects of heading and unintentional impacts, the authors of this study were able to delineate the effects of these two exposures.

As well, they said, the analysis adjusted for relevant covariates, including, for example, neck circumference.

While the study authors acknowledge that the results can't be generalized to younger players outside the northeastern United States, Dr Lingsma and Dr Maas pointed out that the median of three outdoor practices and two outdoor games every 2 weeks reported by study participants "would be comparable to many amateur soccer players in Europe, both adults and children."

The editorial writers noted that the exposures and outcomes were self-reported and measured in the same questionnaire, which might have resulted in reporting bias — with players with CNS symptoms possibly more likely to report more exposure. However, they said, participants had to answer the questions on exposure before questions on outcome, and they couldn't change their answers.

Heading in soccer has not received much attention in consensus statements on concussion in sports, they note.

"Although the current study does not provide evidence to determine whether there is a long-term consequence of heading, it stresses the need to put heading in soccer on the international research and policy agenda."

The study was funded by the National Institutes of Health and the Dana Foundation. Dr Lipton, Dr Lingsma, and Dr Maas have disclosed no relevant financial relationships.

Neurology. Published online February 1, 2017. Abstract, Editorial

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