Aim/objective The objective of this study was to provide a meta-analysis examining the effects of football heading.
Design Meta-analytical review on football heading effects on neurocognitive performance, cognition and symptom reports.
Data sources Combinations of the key terms were entered into the following electronic database search engines: Cochrane Libraries, PyscARTICLE, PyscINFO, PubMed, ProQuest, SPORTDiscus and Web of Science on 7 July 2016.
Eligibility criteria for selecting studies The following inclusion criteria were used to determine eligibility for studies: (1) the study examined and reported on soccer athletes; (2) the population's age, sex and sport position was described; (3) cognitive function, symptoms, balance or other outcomes were quantitatively measured; (4) football heading exposure was quantitatively measured between at least two groups and (5) the study was written in the English language after December 1979.
Results The literature search process identified 467 unique studies. After applying exclusion criteria, 28 studies remained. Included studies had a total of 2288 participants (female participants =933, male participants =1355), aged 13–70 years. The overall results of random effects modelling of football heading were found to be inconclusive across all outcomes, groups and time points. No moderating variables related to methodological, sample or study characteristics were supported in the analysis; age was a potential moderating variable.
Summary/conclusions We provide the first meta-analytical review of football heading effects aggregated from multiple studies and extended findings from a recent systematic review of the effects of football heading. Our analysis indicates no overall effect for heading a football on adverse outcomes.
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Contributors AK designed the work, interpreted data, drafted the Introduction and Discussion, revised the manuscript and approved the final version. RB analysed and interpreted data, drafted the Methods and Results sections, revised the manuscript and approved the final version. SC interpreted data, drafted the Introduction and Discussion sections, revised the manuscript and approved the final version. JMD acquired and interpreted the data, drafted the Methods and Results sections, revised the manuscript and approved the final version. LS acquired and interpreted data, drafted the Introduction section, revised the manuscript and approved the final version. VR acquired and interpreted data, drafted the Abstract, revised the manuscript and approved the final version. MC interpreted data, drafted the Discussion, revised the manuscript and approved the final version.
Funding This research was supported in part by a grant to the University of Pittsburgh from the National Institute on Deafness and Other Communication Disorders (1K01DC012332-01A1).
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.