What does it really mean when you say people live longer because of screening for the disease.
It depends.
I think the point is valid, if all you've done is discovered the disease, as in the example, eight years earlier. If it allows you to kill the disease BECAUSE you've discovered it earlier, not so much. But, it is an interesting point about statistics and medicine. The treatment part is the part that matters, not the ability to detect the disease earlier.
