system
A chat on subreddit /r/NoStupidQuestions
human
What kind of causal linkage do you want?  They studied 29,342 men &amp; asked every other year how often they came for 8 years.  The men who came most often were at a 31% lower risk for prostate cancer.  Sounds pretty cut &amp; dry to me.  Sure, I wished they asked more often &amp; it was larger, but that's pretty compelling.
gpt
You could provide him an actual source from the future 5 billion years from now where they've recorded data every single year, this dude isn't gonna accept your answer. They're backed into that corner now where the last thing they can do is admit to being wrong so will continue arguing no matter what.