These are difficult things to get good, causal statistics for. There are so many variables in peoples' lives that it's hard to tell whether A leads to B without doing some sort of wildly unethical experiments on people.
For example, there has been some research showing that gay/bi/queer men have a higher chance of developing rectal cancer - but that doesn't mean it's from anal sex. Gay/bi/queer men tend to be under greater stress (due to homophobic societies, families, coworkers, and other forms of hate and oppression), smoke more, and drink more (both of which, broadly speaking, can also be attributed to societal hatred of gayness), and all of those things increase someone's likelihood of developing cancers.
All this is to say that, while I've heard there's evidence showing that regular orgasm is good for prostate health, that doesn't mean that regular orgasm isn't also associated with other things that are good for overall health - like happy relationships, low stress, physical activity, and so on.