Immortal words from Tony Hill
Fifty years ago, Sir Austin Bradford Hill stood before the audience of the gathering of the Society of Occupational Medicine and uttered these words. They ring as true today. Where do we go from studying association to causation? He talked of nine viewpoints. These were strong association, consistent association in different types of studies — in his time retrospective and prospective, temporality — that the exposure must precede the disease occurrence, specificity — one exposure for one disease outcome, Biological Gradient — the dose response effect, plausibility — that things could be explained by biological knowledge, coherence — that it should not conflict with what we know, be analogous to other studies with animal studies, and be backed by experimental evidence. The point to note is he never meant any or all of these to be sine qua non or absolute. Yet, fifty years down the down the line, we call them Bradford Hill criteria, :-)
