@article{ref1,
title="Persistent effects of playing football and associated (subconcussive) head trauma on brain structure and function: a systematic review of the literature [soccer]",
journal="British journal of sports medicine",
year="2016",
author="Tarnutzer, A. A. and Straumann, D. and Brugger, P. and Feddermann-Demont, N.",
volume="ePub",
number="ePub",
pages="ePub-ePub",
abstract="AIM/OBJECTIVE: There is ongoing controversy about persistent neurological deficits in active and former football (soccer) players. We reviewed the literature for associations between football activities (including heading/head injuries) and decline in brain structure/function. <br><br>DESIGN: Systematic literature review. DATA SOURCES: MEDLINE, Embase, PsycINFO, CINAHL, Cochrane-CRCT, SportDiscus, Cochrane-DSR=4 (accessed 2 August 2016). ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Original studies reporting on football-related persistent effects on brain structure/function. <br><br>RESULTS from neurocognitive testing, neuroimaging and EEG were compared with controls and/or correlated with heading frequency and/or head injuries. <br><br>METHODological quality was rated for risk-of-bias, including appropriateness of controls, correction for multiple statistical testing and assessment of heading frequency and head injuries. <br><br>RESULTS: 30 studies with 1691 players were included. Those 57% (8/14) of case-control studies reporting persistent neurocognitive impairment had higher odds for inappropriate control of type 1 errors (OR=17.35 (95% CI (10.61 to 28.36)) and for inappropriate selection of controls (OR=1.72 (1.22 to 2.43)) than studies observing no impairment. Studies reporting a correlation between heading frequency and neurocognitive deficits (6/17) had lower quality of heading assessment (OR=14.20 (9.01 to 22.39)) than studies reporting no such correlation. In 7 of 13 studies (54%), the number of head injuries correlated with the degree of neurocognitive impairment. Abnormalities on neuroimaging (6/8 studies) were associated with subclinical neurocognitive deficits in 3 of 4 studies. SUMMARY/CONCLUSIONS: Various methodological shortcomings limit the evidence for persistent effects of football play on brain structure/function. Sources of bias include low-quality assessment of heading frequency, inappropriate control for type 1 errors and inappropriate selection of controls. Combining neuroimaging techniques with neurocognitive testing in prospective studies seems most promising to further clarify on the impact of football on the brain.<br><br>Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.<p /> <p>Language: en</p>",
language="en",
issn="0306-3674",
doi="10.1136/bjsports-2016-096593",
url="http://dx.doi.org/10.1136/bjsports-2016-096593"
}