Why I worry about large international studies

Recently a reader pointed me to a large, international multicentre trial published in a leading medical journal. This type of research is thrust under the noses of doctors and regulators the world over, presented as evidence beyond refute. Research is better than any marketing campaign, and can be worth billions in drug sales worldwide. Here are some words of caution about this evidence.

Large studies are large for one reason only: the impact of the intervention is so small that only a large study will detect it. How large a study was needed to show the …