Digital Public Defence: Stian Bahr Sandmo

MD Stian Bahr Sandmo at Instiute of Clinical Medicine will be defending the thesis Repetitive head impacts in football – quantifying exposure and assessing outcomes for the degree of PhD (Philosophiae Doctor).

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Photo: Amalie Huth Hovland, UiO

The public defence will be held as a video conference over Zoom.

The defence will follow regular procedure as far as possible, hence it will be open to the public and the audience can ask ex auditorio questions when invited to do so.

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Digital Trial Lecture - time and place

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Adjudication committee

  • First opponent: Professor Niklas Marklund, Lund University, Sweden
  • Second opponent: Associate Clinical Professor Margo Mountjoy, McMaster University Medical School, Ontario, Canada
  • Third member and chair of the evaluation committee: Professor II Eirik Helseth, Institute of Clinical Medicine, University of Oslo

Chair of defence

Professor II Iver Arne Langmoen, Institute of Clinical Medicine, University of Oslo

Principal Supervisor

Professor Roald Bahr, Norwegian School of Sport Sciences, Oslo


Football involves voluntary heading and an inherent risk of concussions. The question is: What are the effects on the brain from such exposure? 

To answer this, prospective studies are on the way. Central to this thesis is the study RepImpact, exploring potential neurological effects of repetitive head impacts in youth football. Importantly, however, such studies encounter several challenges when quantifying exposure and assessing outcomes. 

First, accurate exposure data is key to assess risk. Thus, we quantified heading exposure in youth football, observing thousands of male and female players across several age groups. Heading rates were influenced by both sex and age, and heading was a rare event in the age groups currently targeted by injury prevention measures. 

Then, we evaluated the validity of different methods for quantifying heading exposure in RepImpact. First, we evaluated in-ear sensors. Despite inaccurate readings in the laboratory, the sensors could discriminate heading from non-heading events during on-field testing. Still, there was a need for secondary verification (e.g. using video analysis) of headers in real-life settings, making their use highly labor intensive. Consequently, we also evaluated a self-report questionnaire. Substantial measurement errors rendered self-report unable to quantify individual heading exposures. However, it could still identify players belonging to high and low-exposure groups, supporting its potential use in RepImpact.

Last, we explored if headers or accidental head impacts cause structural damage to the brain, detected as an increase in NfL or tau proteins in the blood. There was no evidence of structural brain injury; however, we identified an increase in tau levels in response to high-intensity exercise, highlighting an important limitation for its use.

Ultimately, findings from this thesis pave the way for future studies to settle the question on whether repetitive head impacts in football are harmful for the brain.

Additional information

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Published Dec. 3, 2020 10:28 AM - Last modified Jan. 4, 2021 10:38 AM