*The following is excerpted from an online article posted on HealthDay.
As kids who play football get older, head hits during play become more frequent and harder, researchers report.
"Our findings clearly show a trend of head impact exposure increasing with increasing level of play," said study author Jillian Urban, an assistant professor of biomedical engineering at Wake Forest School of Medicine.
The finding is based on a comparison of head impact frequency and impact force among groups of kids between the ages of 9 and 13 playing football in one youth football organization. Head impacts were tracked during practices and varying levels of competitions over four football seasons.
"By recording more than 40,000 head impacts, this study represents the largest collection of biomechanical head impact data for youth football to date," Urban said in a Wake Forest news release.
In all, the investigators tracked head impacts among 97 players spread across three age levels of play. One group was players aged 11 and under and weighing no more than 124 pounds. Another group was players aged 12 and under, and up to 139 pounds. The third group was players 13 and under, and up to 159 pounds.
All players were outfitted with helmet sensors to record impact type, number and force.
The investigators found that roughly two-thirds of all head impacts actually occurred during practice, rather than games. However, the force of the impacts during games was stronger.
The number of impacts during games was also higher among older kids.
And overall, the oldest group of kids experienced a significantly greater number of head impacts than either of the two younger groups.
"Our results are consistent with prior studies of high school and college athletes showing that head impact exposure increases with increasing age and level of play," Urban said. "But they also show significant differences from one level to the next in a single youth organization.
The study was published in the June issue of the Journal of Neurotrauma.