Actually, they don't. Meet "immortal time bias."
And James Delingpole makes the important connection to climate change: "So Butter is Good For You. Just Like Global Warming, Then."
"Compliance bias" is darn difficult to control for.
Matt Ridley posts a blog entry that is intelligent, balanced, and just so sane. In my experience, that's pretty rare these days.
Needless to say, if borne out in further testing, this could change everything.
By splicing animals together, scientists have shown that young blood rejuvenates old tissues. Now, they are testing whether it works for humans.
As Glenn Reynolds might say, "Faster, please."
The discrepancy between the CDC’s assertion that the flu drugs can prevent complications, hospitalizations and perhaps deaths, and the FDA’s insistence that the drugs have only been shown to cut the amount of time that symptoms persist comes down to how they weigh the evidence. The FDA requires randomized clinical trials, the gold standard of evidence in medicine, while the CDC also relies on non-randomized reports.