Repetitive soccer heading adversely impacts short-term learning among adult women.

Abstract

To determine the impact of 12-month heading exposure on short-term learning. A total of 105 active amateur soccer players, 45 women and 60 men, were administered an EMA-based test of working memory, a version of the two-back, once daily for 14 days. Heading exposure of the participants was assessed using "HeadCount", a validated structured questionnaire at the baseline visits. The short-term rate of learning of each individual is quantified by first fitting a quadratic model to the daily performance on the two-back test over a two-week period, then taking the instantaneous rate of the quadratic function at the 7th test. A linear regression model was used to test the association of heading exposure with rates of learning, including age, sex, years of education and history of concussion as covariates, as well as variables describing soccer play and heading within the two-week period. Sensitivity analyses were performed using different methods for quantifying the learning effects and different transformations on 12-month heading exposure. Greater 12-month heading was associated with lower rates of learning among women (p = 0.008) but not among men (p = 0.74). We have identified evidence for an adverse, albeit subclinical, effect of soccer heading on brain function among young adult players, which selectively affects women in our sample.