Ask the doctors: Heading a soccer ball can cause subconcussive injury

Dear Doctor: My granddaughters are absolutely crazy about soccer. They’re constantly trying to outdo each other with their maneuvers, and now one is trying to learn to “head” the ball. But isn’t that dangerous, especially for girls?

Dear Reader: We’ve long been aware of the risk of head injuries posed by activities like football, rugby, ice hockey and boxing, where jolting physical contact is literally built into the sport. Now soccer, long thought of primarily as a running game, is also getting a second look. Although collisions with other players (and with the occasional goalpost) have been the most visible potential sources of head injury on the soccer field, new research confirms what many have suspected – heading the ball takes a toll on the brain.

A study published last spring found that heading the ball – in which a player deliberately moves into the path of a speeding soccer ball in order to control its trajectory with his or her head – is responsible for a greater number of concussions than is contact with elbows, knees or feet. And according to a study published last summer, the adverse physical effects of that signature move are more pronounced in female soccer players than in their male counterparts.

The earlier study, published last April in the journal Frontiers in Neurology, gathered data from 308 active amateur soccer players, 78 percent of them male. Each player self-reported head impacts and any resulting symptoms during a series of two-week intervals. Players also underwent an in-person neuropsychological assessment during each two-week period. With a total of 741 complete data sets collected over the course of three years, researchers were able to correlate frequency of heading with reductions in attention span and reaction time. They found that working memory was also affected, but to a lesser degree.

The other study, published last July in the journal Radiology, found that heading the ball resulted in alterations to white matter in the brain. When this finding was broken down by the sex of the players, it was revealed that these alterations were more pronounced in the brains of the women in the study than in the brains of the men. White matter, which accounts for half of the human brain, is made up of millions of bundles of nerve fibers. Located beneath the gray matter cortex, they connect the different regions of the brain. The white color is due to myelin, a type of electrical insulation that coats the nerve fibers. Damage to white matter can interfere with the high-speed transmission of electrical impulses in the brain, which can result in impairment to sensory, motor and cognitive function. The researchers refer to this damage as “subconcussive head impacts,” meaning that though these injuries don’t produce immediate or measurable symptoms, as concussion does, the effect can be cumulative and long-term.

Because the impact forces of heading a soccer ball come close to matching a helmet-to-helmet football tackle, U.S. Youth Soccer has banned the practice for players younger than 11 years old. You didn’t specify the ages of your granddaughters, but considering what’s potentially at stake, it’s probably a good idea to check in with their parents on the topic of heading.