Soccer Headers Might Be More Risky for APOE4 Genotype Carriers

The findings of a recent study published in JAMA Neurology provide a first indication that the APOE e4 allele may be associated with adverse cognitive sequelae of subconcussive repetitive head impacts (RHIs) independent of prior concussion, the study team reports. The senior author Dr. Michael Lipton from Albert Einstein College of Medicine, Bronx, New York, cautioned however, that there is not an immediate clinical implication to be expected. Rather, clinical implications might only appear eight to ten years after an individual experiences of repetitive mild traumatic brain injuries such as in chronic traumatic encephalopathy (CTE) as noted in other contact and high-impact sports such as boxing or American Football.

The findings in the present study are based on 352 adult amateur soccer players (mean age, 23 years; 256 men) enrolled in the longitudinal Einstein Soccer Study. They all played the game for more than five years and for more than six months per year. Every three to six months over about five years, players completed a validated, online questionnaire to estimate how many headers they did in a 12-month period that was categorized as low (165 headers per year; quartiles 1 and 2), moderate (638 per year; Q3), and high (2,346 headers per year; Q4).

Verbal memory was assessed at each study visit using the International Shopping List Delayed Recall (ISRL) task from CogState. Prior evidence had  suggested that the APOE e4 allele is associated with worse memory in healthy aging adults. high levels of heading were associated with significantly worse verbal-memory performance. And while there was no main association of APOE4 with verbal memory, there was a significant association of this genotype and soccer heading with performance on the ISRL task. In analyses stratified by APOE4 status, APOE4-positive players had about a fourfold greater deficit in verbal memory associated with high versus low heading exposure and an 8.5-fold greater deficit in verbal memory associated with high versus moderate heading exposure, compared with APOE4-negative players. The impairment was relatively mild, however. On an absolute scale, APOE4 carriers in the highest quartile of heading exposure recalled about one fewer item on the ISRL task compared with those in the other quartiles.

An Editorial in JAMA noted that given the observed impairment was subtle and that the study design was cross-sectional, it is unclear whether these impairments were associated with daily function, were noticed by the participants, or were transitory in nature. Conversely, that an interaction effect could be detected at all in a group of active players provides more credence to the modifying role of APOE e4 on repetitive head injury-cognition associations.