Very few concussions are ever diagnosed by a doctor. It is only the past few years that a doctor 'diagnosis' has become common. This is because teams have had to implement concussion protocols for liability reasons and the movie Concussion.

The risk of undiagnosed concussions or ignored concussions is that the person does not take a break to allow the brain to recover. Studies suggest that those low intensity hits that are repeated (hockey, football, etc) without a break from play or practice are the most dangerous. These are mostly sub-concussive impacts without even a need to shake it off.

I think you need to consider the various peak risks of each activity. No contact hockey reduces the repeated body checks and knock downs from them but leaves you with falls and pucks to the head. So, you have reduced many of the risks. Mountain biking trails have risk levels to consider.

Then, consider whether you have adequate disability insurance compared to the risks you decide to endure. Risks tend to have an exponential increase in long term injury or disability as the intensity increases. A fall at 30 mph is substantially more injury risk than a fall at 20 even though the speed is only 50% more. Add the greater ability to recover from a near fall at 20 vs 30.

So, only you can calculate the risk to you.

btw, I learned that helmet padding has a limited life. Check yours.

Thanks Mark, I appreciate all your advice. Definitely going to invest in a fresh bicycle helmet if I go back to riding this summer.

Erik, I was right about your age when I had my last concussion that did me in and your story really resonated with me, since I used to do some fairly extreme stuff in my late teens and 20s (paragliding, skydiving, dropping cliffs on skis and snowmobiles, downhill mountain biking, etc...)

In addition to all of that I was into martial arts/boxing/kickboxing since my late teens.

Just like you I never had a diagnosed concussion (before this last one) or a hard enough hit to black out, mostly just headaches for a few days after a hard fall/landing or a rough sparring session.

So I went on with my life without worrying too much about it. Looking back at it now I realize that some of the issues that I've had in the past were the result of these concussions that I just shrugged off and moved on (vision issues, sleep issues, etc).

Well, it all caught up to me eventually in a big way. I had a concussion (no loss of consciousness or memory loss) while at a boxing sparring, just a hard hit that "rang my bell". I didn't think much of it at first, but then things started to spiral out of control to a point where I couldn't get out of bed for two weeks.

Things eventually got better after about three months, and I thought that I'm all healed (after all, the doc told me to get back to normal life as did my friends/family) and I went for a fairly easy snowmobile ride with some friends.

Well it turned out not to be such a great idea... Things went to hell for me and it was worse than the initial 3 months...

Now 5 years later I'm still not back to normal and deal with the consequences of not taking it seriously back then.

The point of my story is that you need to take this last concussion as a warning and a learning experience. Trust me when I say that what you've experienced is not even close to how it can be if you keep hitting your head. Your body is telling you something, please listen.

By the way, 99% of doctors have no idea what they are talking about when it comes to concussions, just ask any of the long term users on this forum.