So, this is entirely on anecodotal evidence, but after an incident I had, I started asking every diver I met while traveling and at local meetup groups.
Nearly 100% have said they've either had incidents of extreme tiredness, headaches, some shoulder pain, etc at some point in their diving career. They went on to say that they probably had mild DCS symptoms.
Again, these probably don't qualify as clinical cases, but we know that as we ascend, even slowly, there probably is always some bubbling going on.
I don't claim to be any expert or have any stats on this, but just start asking around yourself. I also am not commenting on the severity of these symptoms. I just choose to use nitrox because I believe it decreases risk given the same profile/time.