Repetitive Head Impacts: What You Need to Know About Sub-Concussions
Should We Worry About Every Bang, Bump, and Boom?
“Let’s make this personal. I played competitive ice hockey from 1999–2012, finishing my career at the collegiate (ACHA) level. Statistically, I sustained about 200 to 500 head impacts per season over 13 years. That’s somewhere between 2,600 and 6,500 head impacts throughout my career, with three known concussions in the mix.
So, am I doomed to a future of dementia or worse, as many media outlets might suggest?
Here’s the short answer: Probably not.”
Throwback video from a few years ago!
Why I'm Pretty Sure I'll Be Okay—and You Can Be Too
Despite the headlines, the science on sub-concussion and repetitive head impacts isn't as conclusive or alarming as some may think. In this blog, we'll dive into:
How we define "sub-concussion."
What we know about repetitive head impacts.
Why I'm not overly concerned about my history of head impacts.
The grand summary and actionable takeaways.
1. How Do We Define "Sub-Concussion"?
To understand "sub-concussion," we first need to define concussion. Within the current classification of traumatic brain injuries (TBI), there are three levels:
Mild TBI (Concussion)
Moderate TBI
Severe TBI
These classifications are based on imaging findings, levels of consciousness, and memory changes. But here's the kicker: within this framework, there is no such thing as a "mild" or "severe" concussion—it's just a concussion.
Concussion diagnosis remains clinical and relatively subjective. There's no gold-standard blood test, imaging, or biomarker to confirm a concussion definitively.
So, if we can't even define a concussion objectively, how can we define something less than a concussion, like "sub-concussion"?
We can't.
Instead, it's more accurate to refer to these as head impacts—because, at this time, "sub-concussion" is a poorly defined and subjective term.
2. What Do We Know About Repetitive Head Impacts?
The research on repetitive head impacts (RHI) is growing, but it's far from definitive. Let's break it down:
The Science So Far
According to a 2018 systematic review:
RHI may cause microstructural changes like white matter alterations, cortical thinning, and brain volume loss.
These structural changes were not linked to neurocognitive deficits, such as memory, attention, or executive function.
““Given the evidence reviewed, we conclude the following: 1) exposure to repetitive hits to the head in sport presents the risk of microstructural and functional changes to the brain in male athletes, and 2) prolonged exposure to repetitive head impacts in sport, for both males and females, should be avoided. Further study is essential to advance our understanding of how exposure to head impacts affects the brains of athletes in the short and long-term.” ”
Significant Limitations of the Research
The same review highlighted significant limitations in the studies:
Small sample sizes and high attrition rates skewed results.
Many studies lacked proper control groups, increasing the likelihood of false positives.
Few studies accounted for confounding variables like substance use or mental health conditions, both of which can affect the brain.
Female and youth athletes were severely underrepresented, limiting the generalizability of findings.
Contrasting Evidence
Other research on repetitive head impacts offers a more optimistic outlook:
Studies on amateur soccer players found no significant changes in brain volume or cortical thickness from heading the ball.
Balance deficits from soccer headers typically resolved within 24 hours.
NCAA football players showed no changes in plasma tau levels, a marker often linked to brain injury, over the course of a season.
Functional imaging (like DTI) has found similar patterns between orthopedic injuries (e.g., ACL tears) and concussions, suggesting that brain changes aren't unique to head impacts.
Bottom Line: While repetitive head impacts might cause microstructural changes, there's no conclusive evidence that these changes lead to lasting neurocognitive deficits.
3. Why I'm Not Worried About My History of Head Impacts
My 13 years of competitive hockey left me with thousands of head impacts, but here's why I'm not losing sleep over it:
Lifestyle Modifications Matter More
While my concussion and head impact history is non-modifiable, my lifestyle today is 100% within my control. The research supports this approach:
A study on former NFL players showed that those who followed these habits had better cognitive and emotional health:
Moderate-to-vigorous aerobic exercise
Resistance training
Mediterranean or high-quality diets
Consistent sleep (6+ hours per night)
The Role of Exercise
Exercise isn't just good for your body—it's essential for your brain. After a concussion, the brain often struggles with blood flow regulation, including:
Cerebral autoregulation (blood pressure control)
Cerebrovascular reactivity (response to CO2 levels)
Neurovascular coupling (directing blood to active brain regions)
Neuroautonomic regulation (balancing sympathetic vs. parasympathetic activity)
Studies on athletes show mixed results on these blood flow mechanisms after a sports season. But what's clear is this: exercise helps. It improves all aspects of brain blood flow regulation, making it a cornerstone of long-term brain health.
Meeting the Basics
The CDC, WHO, and AHA all recommend at least 150 minutes of moderate-intensity weekly exercise. This meets general health guidelines and aligns with concussion recovery protocols.
4. Grand Summary and Takeaways
Here's what we know:
Many contact athletes will experience repetitive head impacts throughout their careers.
These impacts may cause microstructural changes but are not consistently linked to neurocognitive deficits.
The research is still evolving, with limitations in study design and generalizability.
And here's what we can do:
Focus on what's modifiable. Lifestyle habits like exercise, diet, and sleep profoundly impact long-term brain health.
Don't panic. While avoiding unnecessary head impacts is essential, there's no definitive evidence that repetitive head impacts guarantee poor outcomes.
If you're active in sports or have a history of concussions, prioritize your health today:
Move your body.
Eat nutrient-dense foods.
Get quality sleep.
Your brain will thank you!
“If you’re concerned about repetitive head impacts, concussion recovery, or your long-term brain health, I’d love to help. At my clinic, we take a comprehensive, evidence-based approach to assess and address your unique needs—whether you’re an athlete, a parent, or simply someone wanting answers. Don’t wait for symptoms to worsen or questions to go unanswered. Book an intro call today to start your personalized path to better brain health and recovery!”