Soccer is growing in popularity in the US and Canada. While the sport of choice in much of the rest of the world, it took many years before a sizeable population of players and fans could be established in North America for it to take hold. Now that 18 million Americans play soccer every year (with 78% being under 18) research into the concussive forces of heading the ball is being taken more seriously in these countries.
Lipton et al 2011 completed diffusion tensor imaging of soccer players who had played the game for over 20 years. They found that the threshold for the beginnings of mild traumatic brain injury was heading the ball 1000-1500 times in a year.
While this sounds like a high threshold, it is actually quite easy to surpass this number. Assume for a moment someone plays 4 times a week for 6 months of the year. 26 weeks x 4 practices or games = 104 times. Averaging the threshold area to 1250, that would amount to heading 12 times each practice or game. Many players report heading the ball 30-50 times during a warm-up, far surpassing the threshold determined above. While the speed of the ball also plays a factor (it is doubtful that 8 year olds are accelerating the ball to the speed of 100km/hr) This brings to light that this sport, while generally considered non-contact, has the potential to alter brain function and thus the course of the lives of the young players. More research is needed but this is definitely something to keep an eye on in the future.