Smoking and lung cancer: identifying the link

In this Step, we discover how smoking came to be identified as the leading cause of lung cancer. We also consider why this was so important for the development of public health research, policy and practice in the post-war period.

Identifying the link

In the years immediately after World War II, researchers and officials in the Ministry of Health became concerned about growth in the number of cases of lung cancer. Between 1930 and 1945, there was a six-fold increase in lung cancer amongst men aged over 45.¹ To find out what was causing this, the Medical Research Council commissioned the epidemiologists Sir Richard Doll and Austin Bradford Hill to conduct a study.

Doll and Bradford Hill, who were based at the London School of Hygiene & Tropical Medicine, interviewed patients in London hospitals with lung cancer and those who had other kinds of cancer, as well as a control group who were suffering from something other than cancer. Doll asserted that he and Bradford Hill were not expecting tobacco to be involved in causing lung cancer. He said that ‘For my part, I suspected that if we could find a cause it was most likely to have something to do with motor cars and tarring of roads.’²

What Doll and Bradford Hill found, however, was an association between smoking and lung cancer. Of the 649 men with lung cancer who were interviewed, just 0.3% were non-smokers.³ The researchers were initially cautious about their findings, but Doll and Bradford Hill conducted another study a few years later that confirmed a link between smoking and lung cancer, and also showed that the death rate from lung cancer increased in line with the amount an individual smoked.

This was not the first piece of research to suggest a link between smoking and lung cancer. During World War II, Nazi doctors conducted studies which suggested tobacco might be a cause of lung cancer, but this research was dismissed as German medicine was disgraced and discredited by its involvement in the Nazi’s pursuit of racial purity. American research also pointed to a possible connection between smoking and lung cancer, but Doll and Bradford Hill’s work had the most significant, and enduring impact.

Implications for public health

Doll and Bradford Hill’s identification of a link between smoking and lung cancer was crucial to the development of public health in the second half of the twentieth century. They had uncovered a connection between a specific behaviour, in this case, smoking, and disease. This suggested that individual habits, and not the environment, were responsible for ill-health. The implication was that public health policy and practice should thus focus on getting individuals to change their behaviour to improve their health and that of the public more generally. As we will see, Doll and Bradford Hill’s findings about smoking and lung cancer were replicated elsewhere with other behaviours and other conditions, such as diet and exercise and their relationship to heart disease.

The Doll and Bradford Hill study was important in another way too: it helped establish epidemiology and epidemiological evidence as central to our understanding of public health problems. Although the gathering of statistics on population health had long been part of public health practice, this kind of data had not necessarily been used to establish the causes of diseases or suggest what action should be taken to combat them. To understand chronic conditions like lung cancer or heart disease, however, it was necessary to look at long-term trends and multiple potential causes, something epidemiologists were uniquely placed to do.

As the veteran epidemiologist, Jerry Morris, noted in 1957: ‘The main use of epidemiology is to discover populations or groups with high rates of disease, and with low, in the hope that causes of freedom from disease can be postulated.’⁴ What epidemiologists found, as we saw with Doll and Bradford Hill, was that individual behaviour often accounted for these differences. Morris was quite right when he predicted that ‘prevention of disease in the future is likely to be increasingly a matter of individual action and personal responsibility…we must look forward to building a new kind of partnership between community and individual in place of the old where so often in Public Health the community did things for the individual.’⁴