[hef19898]

Then the title is wrong, since colonoscopies actually do increase survival rates (everything would have surprised me a lot as someone who was saved by one), but rather that invitations for colonoscopies don't work. No idea why, but maybe people willing to do one go anyway while those unwilling are very unlikely to follow an invitation. Either way, the title is wrong, misleading and very clickbaity.

[elcomet]

What you're saying is not totally correct. If you look only at patients that did get a colonoscopy, you cannot be sure that it is the colonoscopy that helps, or another variable (those people might monitor their health closer). Your assignment is not random any more so you cannot make any causal statement.