For the last 14 years, fans have voted Dale Earnhardt Jr. the most popular driver in Nascar. The Hendrick Motorsports driver doesn't just move needles, he jolts them: When he announced last December that he would return to racing this Sunday at the Daytona 500, ticket sales immediately spiked. The audience for the television broadcast on Fox will be larger.

Call it the "Dale Earnhardt Jr. Effect." It's real.

Yet the most lasting impact he will make on the sport is hiding in plain sight.

Dale suffered a concussion during a crash last June at Michigan International Speedway. That concussion was (at least) his second in four years. Watch the crash and you might think he didn't hit that hard, but that's the thing about concussions--the impact doesn't have to look bad to be serious. (Sometimes it's the force of your brain shifting inside your skull, not the actual impact.)

After the Michigan race, Dale managed to drive three more races--for a time, he convinced himself his symptoms were caused by allergies or illness--but once diagnosed, he missed the remainder of the season.

And then he did what many drivers in his place might not have done. In a sport that requires athleticism, skill, preternatural spatial awareness...and the ability to look past the inherent risk of driving a race car at 200 miles per hour and still perform at the highest level, he talked about his injury.

He talked about his symptoms. He talked about the pain and the dizziness. He talked about his rehab and recovery.

"I was pretty transparent during the entire process," he told me earlier this week, "and in some ways, that was for my own peace of mind. I didn't want people wondering. I decided to help people understand what I was dealing with, and how bad this is. My doctors also said I needed to keep my stress levels low because that would help my recovery. Talking about it was a way to stress about it less, for me to worry less about the people who were wondering about me and worrying about me.... Talking about it and showing people how I was doing meant they could relax. That meant I could relax too."

Talking about head injuries is something most athletes typically avoid. Talking about head injuries is something most people in general avoid. The macho move is to shrug it off.

Take me. I grew up in a time when getting your bell rung was a badge of honor: You wore it and moved on. Between contact sports and wrecking motorcycles and bicycles and other misadventures, I've seen stars, been knocked out, had headaches and nausea that lasted for days...and those were just the concussions I knew about. And it gets worse. CTE (chronic traumatic encephalopathy, a progressive degenerative disease caused by a severe blow or repeated blows to the head) can result from impacts that don't even reach the concussion level.

If ignoring concussions was par for the course for me, think of how it is for a professional athlete who plays a contact sport. The pressure is enormous. You have to shrug it off. You have to get back out there. You have to pretend that you're OK.

If you're not in the car, or on the field, you can't perform--and that means someone else will take your place.

But, slowly, that's changing. Football players who stepped forward to talk about their own experiences have made it a little easier for other players to talk about their symptoms, and to seek proper treatment.

The same change will now start to happen in Nascar. Some drivers--not all, but some, because major cultural shifts are always gradual--will feel less need to pretend they're OK.

After all, the most popular driver in the sport admitted he had a concussion and took the necessary time off to recover. And he waited--because with concussions, time is part of the recovery process--until he was medically cleared to race again. He set an example that will be hard for others to ignore.

The sport continues to make strides in dealing proactively with head injuries. Last week, Nascar updated its concussion protocol, requiring doctors at every track to use the same concussion test, expanding the use of on-site neurological consultants, and broadening the guidelines for when drivers must visit the infield care center after a crash.

But the biggest change will occur when drivers--and athletes in other sports--feel comfortable stepping forward. Dale is hoping to lead that change because he feels he has a responsibility to improve the sport. And, like many athletes, he plans to donate his brain to concussion research.

"When I stop driving, I want the sport to be as healthy as it can be," he says. "Now I try to think of what is the best thing for the sport instead of just the best thing for me. We're going through a big transition in how we talk about concussions and how we treat concussions. I want to be a part of that."

Yet the impact of those conversations will be much broader than just within the sport. Because they have followed Dale's journey back to the track, millions of fans now think more about concussions. They're smarter. They're more informed. They have a better sense of what to look for if their children suffer head injuries. They know to take concussions seriously, possibly even more seriously than some other injuries.

After all, a pulled muscle heals. A broken bone heals.

Sometimes, a head does not heal.

Now, more people know that.

Someday, a driver will crash into a wall at 200 miles per hour. That driver will be evaluated by a skilled physician and may be required to skip a number of races. He or she will be disappointed...but won't try to shake it off. Getting back in the car too soon after suffering a concussion would be stupid.

Someday, a father will see his daughter clash heads with another soccer player. Without thinking, he'll have her evaluated by a trained professional. He won't tell her to just shake it off. That would be stupid.

Someday, everyone will realize that, like a broken bone, you don't just shrug off a head injury. You treat it.

How does that happen? Data and research and scholarly journals are great, but people like Dale, people with a pubic platform willing to talk openly about their experiences, spread awareness and create change at a much faster rate than would otherwise have been possible.

Dale's place as an iconic figure in racing is already assured, but his real legacy will transcend sports.

Someday, racing historians will look back and see Dale's concussion--and, more importantly, that he chose to deal with it publicly--as a turning point in the way the sport treats head injuries. On a broader level, he will be seen as just one of many who stood at the forefront of a broad cultural change, one that eventually affected the health and lives of millions of people.

Wins, awards, accolades...those are what fans tend to remember, but ultimately what we do for other people is what truly matters.

Give a quick mental nod of thanks to people like Dale who are willing to help make a difference, and then go a step further. Decide how, in whatever area you choose, you will make a small difference.

And then go make it. Someday, when you look back, the difference you made in the lives of other people is what will make you feel your life was truly worthwhile.