Repeated heading and accidental head impacts in football cause changes to blood patterns in the brain, potentially interfering with signalling pathways, according to a study of players in Norway.
The peer-reviewed research, published in the Brain Injury journal, is the latest item in a growing body of evidence pointing to the dangers of heading. It discovered “specific alterations” in levels of microRNAs in the brain upon analysing blood samples from 89 professional players in the country’s top flight.
MicroRNAs are molecules that help to regulate gene expression, through which DNA instructions are converted into products such as proteins, in bodily fluids. The findings suggest that, given the change in levels, they may be able to be used as biomarkers to detect brain injury.
Blood samples were taken from players after accidental head impacts in matches and after specifically designed training sessions. Forty-eight of the players, drawn from three teams, took part in a session that included repetitive heading drills from set pieces and similar scenarios; they also undertook one that involved other high-intensity exercise, with no head contact allowed. The results found specific changes in certain microRNA levels whose numbers were unaffected by the other high-intensity exercise.
Accidental head injuries were found to alter the levels of eight microRNAs that high-intensity exercise did not affect, and repetitive headers were found to change six. The upshot is that, as well as potentially detecting brain injury, microRNAs may also be able to differentiate injury severity.
Stian Bahr Sandmo of the Oslo Sports Trauma Research Centre at the Norwegian School of Sport Sciences, which led the study, said: “This is a relatively small sample-size exploratory study but future findings expanding upon our research could ultimately lead to an improved understanding of the potential hazardous effects of repetitive head impacts.”
The risks involved with heading have become a major talking point in football. New guidance was issued in July to limit players in the Premier League and Football League to 10 “higher force” headers in training sessions, although there is doubt over whether those guidelines are being followed and Nuno Espírito Santo publicly admitted ignoring them during his short time as Tottenham manager. Concussion substitutes have also been trialled in English football, allowing two replacements for players who have sustained head injuries.