Heading a soccer ball is common practice in any game, particularly during the crucial moments when a snap opportunity arises to score a goal. However, researchers have found that heading a ball anywhere between 6 to 12 times during a single game is enough to cause brain damage over time.

Researchers found that head ballers showed changes in the white matter of their brain that resemble damage seen in traumatic head injuries. The white matter is the communication network in the brain; it sends messages between neurons (gray matter).

In addition, these soccer players face a higher risk of developing thinking and memory problems. The researchers chose to examine soccer players, as it the world's most popular sport with more than 265 million players, and they wanted to see if there was any unknown risks involved.

"We looked at the relationship between heading and changes in the brain and changes in cognitive functions [thinking and memory], and we found that the more heading people do, the more likely we are to find microscopic structural abnormalities in the brain, and they're more likely to do poorly on cognitive tests, particularly in terms of memory," said study author Dr. Michael Lipton, associate director of the Gruss Magnetic Resonance Research Center at Albert Einstein College of Medicine and medical director of magnetic resonance imaging at Montefiore Medical Center, both in New York City.

However, the sample size of the study group was small with just 37 men and women who played soccer since they were children. The study noted that soccer players head the ball six to 12 times during games, where balls can travel at speeds of more than 50 mph. During practice drills, players commonly head the ball 30 or more times.

This isn't the first study to link heading and changes in the white matter in the brain. In an issue of the Journal of the American Medical Association in November last year, Harvard researchers compared soccer players to swimmers, and found changes in the white matter in soccer players. Meanwhile, another study published in Pediatrics this month showed that children who sustain multiple brain injuries, like concussions, may take longer to recover than those who have only had one incident.  Subjects who had a concussion before being admitted to the ER for another concussion had symptoms 24 days out, compared to 12 days for patients who only had one concussion their whole lives. The time period extended for patients who had more concussions in their history.

The findings were published online in the journal Radiology.