A blood protein being investigated as a possible concussion biomarker varied with sex and sport participation even among uninjured teenagers.
In 120 Canadian adolescent athletes, researchers found that these background characteristics mattered when interpreting plasma brain-derived neurotrophic factor, or BDNF.
What researchers studied
The researchers examined whether circulating BDNF levels were associated with demographic and sport-related characteristics. BDNF has attracted attention as a potential indicator in sport-related concussion research, but normal variation could make it harder to interpret.
The cross-sectional analysis was nested within a multisite Canadian sport cohort and included 60 uninjured male and 60 uninjured female participants.
Their average ages were approximately 15.8 and 16.0 years, respectively.
Researchers measured plasma BDNF and considered sex, age, body measurements, previous concussion, menstrual-cycle phase and whether participants played non-contact, contact or collision sports.
What they found
BDNF levels were higher in male participants, with a reported regression coefficient of 0.176 and a 95% confidence interval from 0.010 to 0.342.
Among female participants, increasing age was also associated with higher BDNF, with a coefficient of 0.089.
Contact-sport participants had lower levels than non-contact-sport participants, with a coefficient of −0.462 and a 95% confidence interval from −0.830 to −0.093.
Previous concussion history was not significantly associated with plasma BDNF in this sample: the reported coefficient was −0.149, with a confidence interval crossing zero.
Menstrual-cycle phase and body mass index likewise did not show statistically significant associations.
What it means
A useful clinical biomarker must be interpreted against an appropriate reference range.
These findings suggest that future concussion studies may need to account for sex, age and type of sport when assessing BDNF levels.
The result is about variation in a candidate blood measurement, not about a validated test.
It does not establish that BDNF can diagnose a concussion or guide decisions about an athlete returning to play.
Important limitation
All blood samples were collected from athletes without an active injury at one point in time.
The sample was relatively small and cross-sectional, so the study could not track BDNF changes after concussion or establish whether any observed difference was caused by sport participation.
Source Information
Study: Factors influencing plasma brain-derived neurotrophic factor (BDNF) in adolescent sport participants
Authors: Nikolas O. Josafatow-García, Jason B. Tabor, Linden C. Penner, Jean-Michel Galarneau, Douglas D. Fraser, Carolyn A. Emery, Cheryl Wellington and Chantel T. Debert
Journal / Source: Scientific Reports
Published: 2 November 2026
