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Updated: Mar 8, 2026
In Vivo Protocol of Controlled Subconcussive Head Impacts for the Validation of Field Study Data
Published on: April 18, 2019
Symptoms from repeated intentional and unintentional head impact in soccer players
Walter F Stewart1, Namhee Kim1, Chloe S Ifrah1
1From Sutter Health Research (W.F.S.), Walnut Creek, CA; The Gruss Magnetic Resonance Research Center (N.K., C.S.I., T.A.B., M.L.L.), the Departments of Radiology (N.K., C.S.I., T.A.B., M.L.L.), Neurology (R.B.L., M.E.Z.), Epidemiology and Population Health (R.B.L., M.K.), and Psychiatry and Behavioral Sciences (M.L.L.), and The Dominick P. Purpura Department of Neuroscience (M.L.L.), Albert Einstein College of Medicine and Montefiore Medical Center; and Fordham University (M.E.Z.), Bronx, NY.
Objective:
To determine the rate and differential contribution of heading vs unintentional head impacts (e.g., head to head, goal post) to CNS symptoms in adult amateur soccer players.
Methods:
Amateur soccer players completed baseline and serial on-line 2-week recall questionnaires (HeadCount) and reported (1) soccer practice and games, (2) heading and unintentional soccer head trauma, and (3) frequency and severity (mild to very severe) of CNS symptoms. For analysis, CNS symptoms were affirmed if one or more moderate, severe, or very severe episodes were reported in a 2-week period. Repeated measures logistic regression was used to assess if 2-week heading exposure (i.e., 4 quartiles) or unintentional head impacts (i.e., 0, 1, 2+) were associated with CNS symptoms.
Results:
A total of 222 soccer players (79% male) completed 470 HeadCount questionnaires. Mean (median) heading/2 weeks was 44 (18) for men and 27 (9.5) for women. One or more unintentional head impacts were reported by 37% of men and 43% of women. Heading-related symptoms were reported in 20% (93 out of 470) of the HeadCounts. Heading in the highest quartile was significantly associated with CNS symptoms (odds ratio [OR] 3.17, 95% confidence interval [CI] 1.57-6.37) when controlling for unintentional exposure. Those with 2+ unintentional exposures were at increased risk for CNS symptoms (OR 6.09, 95% CI 3.33-11.17) as were those with a single exposure (OR 2.98, 95% CI 1.69-5.26) when controlling for heading.
Conclusions:
Intentional (i.e., heading) and unintentional head impacts are each independently associated with moderate to very severe CNS symptoms.
