Denominators

In my City AM column today, I start with Richard Doll's research into smoking before discussing vaccine efficacy and our current obsession with the number of Covid deaths. The common denominator is denominators.

In the late 1940s, Austin Bradford Hill and Richard Doll began interviewing hundreds of hospital patients, half of whom had lung cancer while the other half had various other diseases. Their research, published in 1950, showed that 99.7 per cent of the male lung cancer patients had a history of smoking. Out of 649 patients, only two were nonsmokers. In retrospect, it seems amazing that no one had spotted the link between smoking and lung cancer before, but it is less surprising when you consider that 94.8 per cent of the men who were not in hospital with lung cancer also had a history of smoking. 

This might not seem like such a big difference. The vast majority of the men in hospital had smoked tobacco, regardless of what they were being treated for. And yet a statistician can tell from the figures above that smokers were fourteen times more likely to get lung cancer than nonsmokers.

Have a read.