We need to train how much exercise affects each blood-based brain measurement for concussion

Effects of physical exercise on early changes in blood-based brain biomarkers: implications for the acute point-of-care diagnosis of concussion

Bazarian J, Abar B, Merchant-Borna K, Pham DL, Rozen E, Mannix R, Kawata K, Chou YY, Stephen SJ, Gill J. J Neurotrauma. October 6, 2022. doi: 10.1089/neu.2022.0267. E-publishing prior to printing. PMID: 36200628.

https://www.liebertpub.com/doi/10.1089/neu.2022.0267

Take home message

Physical exercise can change some blood-based brain measurements that researchers hope can help clinicians objectively diagnose a concussion.

Background

An objective tool such as a blood-based biomarker (measures) could help diagnose acute concussion. However, many blood biomarkers associated with brain inflammation can change as a result of physical exertion. Therefore, we need more information about whether and to what extent the change occurs during military and sporting events to make clinical decisions.

Study aim

The authors assessed four blood-based biomarkers before and after a single workout of aerobic and resistance exercise to determine how these biomarkers changed after physical activity.

Methods

The authors recruited 30 collegiate football players (~19 years old). Fifteen players underwent diffuse tensor imaging 24 hours before and 48 hours after strength training and aerobic exercise. Blood was collected immediately before imaging and then again immediately after exercise and 45 minutes later. The authors analyzed the blood for four biomarkers: 1) glial fibrillary acidic protein (GFAP), 2) ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1), and 3) neurofilament light (NFL), and 4) tau. Players wore body sensors during training to measure distance (km), energy expenditure (kcal), player load (the sum of all three acceleration planes) and work ratio (% of time moving >1.5 m/sec) . On average the training sessions lasted 90 minutes.

Results

Overall, two blood-based biomarkers changed after physical activity, and two did not. Specifically, GFAP decreased (median decrease 28%) immediately after physical activity compared to baseline and returned to baseline within 45 minutes. In contrast, UCH-L1 was not immediately different from before exercise, but increased within 45 minutes after exercise (median increased by 37%). The changes in these first two biomarkers related to the duration of exercise. Specifically, a person would experience more biomarker changes if they trained for longer. The authors observed no differences over time for NFL, tau, or imaging results.

Viewpoints

The results suggest that just one bout of physical exercise initiates changes in some blood-based brain proteins without altering white matter integrity. This finding suggests that changes in the levels of two blood-based biomarkers are not due to white matter changes. The authors suggested that when commercial kits become available for physicians to assess concussions, we may need to use a comparison to take into account the duration of training. This adjustment may not be necessary if the UCH-L1 is evaluated immediately after a concussion or if the GFAP test occurs after a sporting event (after the patient has rested for 45 minutes). Furthermore, tau and NFL remained fairly stable over time; However, the authors acknowledged that these two biomarkers are less diagnostic during the first few hours after a concussion.

Clinical implications

Medical professionals should continue to use multiple tests to make decisions about the diagnosis of an acute concussion. In addition, they should be aware that more reliable, objective diagnostic tests will soon come to the market, but we should consider optimizing their accuracy.