according to authors of a recent longitudinal study. Worse verbal memory was linked to high levels of ball heading among those players who were APOE e4–positive, compared with those who were APOE e4–negative, according to the authors, led by Liane E. Hunter, PhD, of the Gruss Magnetic Resonance Imaging Center at Albert Einstein College of Medicine, New York.
These findings, while preliminary, do raise the possibility that “safe levels for soccer heading” could be proposed to protect players from harm or that APOE e4-positive players might be advised to limit their exposure to head impacts, Dr. Hunter and coauthors wrote in a report in JAMA Neurology.
However, the findings should “in no way” be used to justify APOE testing to make clinical decisions regarding the safety of playing soccer, said Sarah J. Banks, PhD, of the University of California, San Diego, and Jesse Mez, MD, of Boston University in a related editorial (doi: 10.1001/jamaneurol.2019.4451). “Like most good science, the study provides an important, but incremental, step to understanding gene-environment interactions in sports,” Dr. Banks and Dr. Mez wrote in their editorial.
While there are some studies tying APOE e4 to poorer neuropsychiatric performance in boxers and U.S. football players, there are no such studies looking at the role of APOE e4 in soccer players exposed to repetitive “subconcussive” ball heading, according to Dr. Hunter and coresearchers. Accordingly, they sought to analyze APOE e4 and neuropsychological performance in relation to ball heading in 352 adult amateur soccer players enrolled in the Einstein Soccer Study between November 2013 and January 2018. About three-quarters of the players were male, and the median age at enrollment was 23 years.
The players completed a computer-based questionnaire designed to estimate their exposure to soccer heading at enrollment and at follow-up visits every 3-6 months. To test verbal memory at each visit, players were asked to memorize a 12-item grocery list, and then asked to recall the items 20 minutes later.
High levels of heading were linked to poorer performance on the verbal memory task, similar to one previously reported study, investigators said.
There was no association overall of APOE e4 and heading with performance on the shopping list task, according to investigators. By contrast, there was a 4.1-fold increased deficit in verbal memory for APOE e4–positive players with high heading exposure, compared with those with low exposure, investigators reported. Likewise, there was an 8.5-fold increased deficit in verbal memory for APOE e4–positive players with high versus moderate heading exposure.
That said, the absolute difference in performance was “subtle” and difficult to interpret in the context of a cross-sectional study, Dr. Banks and Dr. Mez said in their editorial.
In absolute terms, the mean decrease in scores on the 13-point shopping list task between the high and low heading exposure was 1.13 points greater for the APOE e4–positive group, compared with the APOE e4–negative group, and the decrease between the high and moderate heading exposure groups was 0.98 points greater, according to the report.
“The effect size of our interaction is relatively small,” Dr. Hunter and colleagues acknowledged in their report. “However, similar to the widely cited model of disease evolution in Alzheimer disease, our findings may be evidence of early subclinical effects, which could accumulate in APOE e4–positive players over a protracted time frame and ultimately be associated with overt clinical dysfunction.”
Several study authors said they had received grants from the National Institutes of Health and affiliated institutes, the Migraine Research Foundation, and the National Headache Foundation. They reported disclosures related to Amgen, Avanir, Biohaven Holdings, Biovision, Boston Scientific, Eli Lilly, eNeura Therapeutics, GlaxoSmithKline, Merck, and Pfizer, among others.
SOURCE: Hunter LE et al. JAMA Neurol. 2020 Jan 27. doi: 10.1001/jamaneurol.2019.4828.