Most MMA athletes aren't bashing eachother's skulls in during training..... Brain damage and career/body longevity has been a long standing concern, where you see the majority of camps pulling back on the amount of hard sparring. In this day and age it's considered relatively crude for a school to do a consistent amount of hard sparring. There's usually a common rule that you shouldn't go blasting people's heads off during training..

Regardless of the answer, there is a reason not many MMA fighters or boxers are in as good a shape at 80 as kung fu practitioners are.

Obviously.... someone who competes in bouts is way more likely to sustain damage..... It's all about how you train. To say all MMA fighters do is spar hard and KO each other during training would be ignorant. "Improve the software without damaging the hardware."

If I get in a real attack, I am pretty sure I could live...

Most people survive non weapon attacks. The amount of damage sustained is a different story.