MRC Integrative Epidemiology Unit (IEU) Seminar Series

Title: “In occupational medicine our object is usually to take action” in order to prevent, as opposed to belatedly observe, harm. (Bradford Hill)

Abstract: 

“In occupational medicine our object is usually to take action” in order to prevent, as opposed to belatedly observe, harm. (Bradford Hill)

Sir Austin Bradford Hill, then Chief UK Medical Statistician, was addressing his fellow Occupational Physicians in early 1965 about the experiences and insights he had gained from the early years of the tobacco controversy. This controversy had broken out in 1950 when he and Richard Doll had concluded that they had found a “real association between carcinoma of the lung and smoking” in their study of British doctors. They were not immediately popular with the UK medical establishment, partly because most of the male doctors (as well as statistics pioneer, Fisher) were then smokers.

However, by 1957, the UK Medical Research Council had concluded, on the basis of additional positive evidence, that “a major part of the increase (in lung cancer) is associated with tobacco smoking, particularly in the form of cigarettes…..the most reasonable interpretation of this evidence is that the relationship is one of direct cause and effect”.

Both the MRC and the later 1964 US Surgeon General reports considered association and causation as part of a continuum: “does the association have a causal significance?”. The dichotomous formulation by Bradford Hill in his 1965 paper  “association or causation”, has arguably encouraged sceptical scientists to withhold a verdict of causation until the evidence is very strong, by which time only some late harm can be prevented, instead of the earlier harm that action on reasonable and “fair”  evidence would have prevented.

This presentation will review Bradford Hill’s 9 “features of evidence” that can help us move from an observed association to a robust causal inference in light of today’s knowledge of multi-causality & complexity;  and apply them to two current controversies, Aerotoxic Syndrome;  and head tumours from mobile phones.

 

All welcome