Everyone loses their first class medical eventually, it's preferable to lose it at 65 versus 45 or 55. What are the most frequent causes for loss of medical prior to 65?

I would like to know in order to take preventative action. I don't want to end up on that list, I doubt anyone intentionally sabotages their own health.

I would suspect diabetes, cancer, or heart conditions, but what are the real-life circumstances that have ended 121 flying careers?