What happens after a concussion, and could its effects linger far longer than most people realize? In this episode, Dr. Donald Redelmeier discusses what population-based research reveals about the lasting effects of concussion for some patients, from traffic risks to long-term recovery and disability.
What happens after a concussion, and could its effects linger far longer than most people realize? In this episode, Dr. Donald Redelmeier discusses what population-based research reveals about the lasting effects of concussion for some patients, from traffic risks to long-term recovery and disability.
Dr. Donald Redelmeier received his MD from University of Toronto, completed postgraduate training at Stanford, and obtained a Masters degree in Health Services Research as a Robert Wood Johnson Clinical Scholar. His research spans a variety of areas emphasizing the psychology of decision making and the epidemiology of motor vehicle trauma. Dr. Redelmeier serves as a Professor at the University of Toronto; a Senior Scientist at the Sunnybrook Research Institute; a Senior Scientist at ICES; and a Staff Physician in General Internal Medicine at Sunnybrook (Canada’s largest trauma hospital).
Resources
ICES | Prior concussions and risk of disability for patients after a motor vehicle crash
Misty Pratt
Concussions are often described as mild traumatic brain injuries, but growing research suggests their effects may be anything but mild. Today, we're joined by Dr. Donald Redelmeier, a senior scientist at ICES and Sunnybrook Research Institute, whose research has explored what happens in the months and years after a concussion. Through large population-based studies using ICES data, Dr. Redelmeier and his colleagues have examined whether a history of concussion is linked to an increased risk of motor vehicle crashes, and whether concussion may influence long-term disability following serious injuries. His work is helping to reshape how clinicians, patients, and policymakers think about recovery. Raising important questions about driving safety, neurocognitive resilience, and the lasting consequences of brain injury. Don, thank you for joining us today on In Our VoICES.
Don Redelmeier
Thanks very much for having me.
Misty Pratt
To start, what motivated you, or what made you want to study the aftermath of a concussion?
Don Redelmeier
I find concussions are a very intriguing type of illness, simply because they're so invisible. If there's obvious blood or vomiting, that's pretty straightforward. People know what's going on. People start to adjust accordingly, but concussions are one of these invisible injuries where compensation is not so perfect. Another nuance is that every concussion is just so different. It depends on the force, the location, the angularity. So, the concussion that you had five years ago may be nothing like the concussion that you have today.
Misty Pratt
And were you seeing a lot of concussion patients where you practiced?
Don Redelmeier
Oh, you betcha! I work at Sunnybrook Hospital, Canada's largest trauma center, and I see a lot of patients with a concussion, and a lot of patients where the concussion is never recognized, i.e. some individual who falls and breaks their hip, oh, we pay a lot of attention to the broken bone. It shows up spectacularly on the medical imaging, but the concurrent concussion is often missed, and yet it can contribute to many problems like delirium.
Misty Pratt
Your first study looked at the link between a diagnosed concussion and car crashes. So, what did that study show?
Don Redelmeier
Well, the main finding was of a significant increased risk of a subsequent traffic crash, particularly during the first month of recovery. About a sixfold increase, which is substantial, far greater than we anticipated. It wasn't unique to being a driver, it also extended to pedestrians during their first month of recovery. So there is an issue about looking both ways when you cross on the street. And the further nuance was that repeated concussions were, of course, even worse than a single concussion, a double concussion, say but that was associated with a more than a 100% increased risk of a subsequent traffic crash.
Misty Pratt
And was this surprising to you, or did you expect these findings given what you see?
Don Redelmeier
I sort of had an edge. What surprised me the most was was the magnitude of increased risk, much larger than we found with epilepsy or sleep apnea, which are already recognized as a risk factor for traffic crashes.
Misty Pratt
Okay, so your second study on disability after crashes suggests that the effects of a concussion may extend well beyond the initial recovery period. When you talk about disability, what types of conditions are you referring to?
Don Redelmeier
Yeah, this is sort of a new way that we have of looking at ICES data, not just for mortality, not just for morbidity, but if an individual is seriously incapacitated, often from a combination of things. All right, so it's not just the concussion, but it also throws off your management of diabetes or depression or degenerative joint diseases of the spine. Well, you've got to apply for disability, and there are a bunch of forms there that your family doctor has to fill out. And when your family doctor does so, there's a special code that shows up in our databases, no different than the code for doing an appendectomy or a hysterectomy, and it's that those objective codes are what we can take into account in our super large database analysis.
Misty Pratt
Would the code then be for the concussion, or would the code be related to something else that would lead to the long-term disability?
Don Redelmeier
We've got both codes, and we knit them together. So, we've got specific codes for the concussion, and then other codes for applying for the disability support program.
Misty Pratt
When you take both of those studies together, what overarching message do you think that they both send about the long-term consequences of concussion?
Don Redelmeier
I mean, put simply, concussions just are not good for you. They both increase your likelihood of a subsequent traffic crash, as well as they increase the severity of a subsequent traffic crash. All right. So, both the risks and the consequences, the repercussions, go up.
Misty Pratt
So it's how bad the crash could be.
Don Redelmeier
Yeah.
Misty Pratt
Okay.
Don Redelmeier
I.e. some crashes are they do a lot of fender damages, but you know you're going to be okay. Whereas other crashes are a whole different element. And gosh, you were just never the same after the traffic crash a few years ago.
Misty Pratt
Did the findings then from that first study on traffic crash inspire the disability study, or were both projects conceived at the same time as part of a larger research project?
Don Redelmeier
One inspired the other. After we found such a large increase in the frequency of subsequent traffic crashes, we absolutely wanted to double check on the magnitude of the average crash. And all this was fueled by what I consider the misleading metaphor of James Bond, who is knocked out in one scene and is cracking jokes in the next, and it leads to this very faulty impression of concussions being innocuous injuries.
Misty Pratt
Yeah, I think to my own experience, I had a child with a concussion, and some of the older advice was actually that she should have spent a lot of time resting in a dark room and all that kind of stuff. Is it changing a little bit more now, where there's different advice for people that they should maybe be jumping back into activities quickly?
Don Redelmeier
Those guidelines have certainly been modified. All right, in terms of return to school, return to work, return to play-all very valuable. This research, though, contributes to a new line, i.e. return to traffic. Does not mean that you have to spend all day at home. It does mean, though, you have to be much more mindful on the roads, all of the sloppiness that we normally get away with, ah, that can you know catch up to you in traffic.
Misty Pratt
Yeah, your reaction times might be very different.
Don Redelmeier
Your reaction times, your awareness of what's going on. Like many people, they sort of bury their noses in their cell phones and they get away with it because of their peripheral vision or some other cues, and that's sort of what gets compromised when you're recovering from a concussion.
Misty Pratt
You discussed the idea of reduced neurocognitive reserve as a possible explanation for your findings. Could you explain to listeners a bit more about what that is and how it may affect the injury.
Don Redelmeier
Okay, so that's a question about scientific theory, and I apologize in advance about how long this response is going to be, all right.
Misty Pratt
All good.
Don Redelmeier
You know, there's all sorts of neurons in my brain. There are about 80 billion neurons in the average brain. All right, almost as many neurons in the brain, as there are stars in the galaxy, and each one of those billion neurons has a different job to do. Like there's a little neuron over here that remembers my wife's birthday, and a little neuron over here that remembers my daughter's birthday, and I must not forget either of those two events. All right, and that's what makes the brain very different from the liver. The liver also has about 80 billion cells in it, but each cell is sort of doing the same thing, right? So that if I lose like a couple of 100 liver cells, no big deal. There's lots of reserve capacity that can take over the same job, and I will never notice the difference. Whereas if I lose 100 neurons, that can really make a difference, even if it just means less reserve capacity when I'm old and gray.
Misty Pratt
Okay, so we're looking at longer term, like way down the road this could have an impact.
Don Redelmeier
We've done other research here at ICES about concussions and the risk of subsequent dementia, and lo and behold, there is certainly an increased risk.
Misty Pratt
Do you think that then a history of concussion should become part of either both trauma assessment and perhaps even other just regular healthcare by asking people about whether concussion has happened in the past?
Don Redelmeier
It should be part of a standardized psychiatric assessment, or neurology assessment, geriatrics assessment, or really any other circumstance where a patient just is not thinking straight. Ask about like an acute concussion but also ask about remote concussions. They may be yet another predisposing factor that is limiting a patient's ability to bounce back.
Misty Pratt
And by remote concussion, you mean something one that may have happened a long time ago?
Don Redelmeier
Yeah, I mean we just don't know if there's any statute of limitations there. But from a physiologic perspective, you know, neurons just do not grow back inside the brain, unlike the cells of the liver that will come back, will regenerate over time.
Misty Pratt
And I mean, you may not be able to answer this, but what about those people who have had bad falls, maybe on their head, never went to a doctor, never got assessed. Should they also maybe be thinking, I might mention this to my care provider?
Don Redelmeier
It's worth mentioning. It's not worth obsessing over, of course, but you know. But the issue is that it underscores the huge importance of preventing the concussions in the first place.
Misty Pratt
Do you think concussion management guidelines should include driving restrictions?
Don Redelmeier
Restrictions are a little bit too draconian, right? Because these risks also extend to pedestrians. No, instead, I mean, I think it's a huge role for awareness and public education, particularly during the first month of recovery. That is not when you want to complicate your situation with a second injury,
Misty Pratt
And what specific advice then would you suggest physicians give patients before they return, not just as you said to driving, but even just regular, you know, within areas where there's heavier traffic, where I'm walking as a pedestrian?
Don Redelmeier
Road safety is just super-duper important. All right, this is the time to avoid high-speed trips late at night when the weather is terrible and the roadways are bad.
Misty Pratt
And maybe take the bus?
Don Redelmeier
Take the bus or just watch some Netflix at home. You are not James Bond.
Misty Pratt
We want to be, but yes. So, what is next then for you in this line of research? Are you looking at anything else related to concussion and recovery?
Don Redelmeier
You betcha. But I'm so cautious about speaking to the media before any study has gone through scientific peer review. My aphorism is that we will sell no wine before it's time. So you betcha that I'm super active. In fact, some of your questions even today are going to help steer my current research project. But those details are not yet ready for public consumption.
Misty Pratt
Okay. Well, we will have to look forward to those. I am very excited to talk to you and maybe do a bit of an update down the road.
Don Redelmeier
Happy to be invited back.
Misty Pratt
Well, thank you so much for being here today. Thanks for joining me for this episode of In Our VoICES. Check out the show notes for links to research and any other information that we've referenced in this episode. A reminder that the opinions expressed in this podcast are not necessarily those of ICES. Please be sure to follow and rate us on your favorite podcast app. If you have feedback or questions about anything you've heard on In Our VoICES, please email us at communications@ices.on.ca, and we will get back to you. All of us at ICES wish you strong data and good health.